With the recently found INVLPGB / TLBSYNC issue, there has been some
interest in disabling INVLPGB-based TLB flushing, in order to rule out
that CPU issue as a cause of userspace crashes.
Add a kernel command line option to control the TLB flushing behavior.
If the need arises, we will add a "tlbi=broadcast" for the case when TLB
invalidation broadcasts need to be explicitly selected, but this is not
needed now yet.
[ bp: Rewrite commit message, move to cpu/common.c, add documentation. ]
Fixes: 767ae437a3 ("x86/mm: Add INVLPGB feature and Kconfig entry")
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260729204341.3eb0b5ea@fangorn
- fix a lot of small bugs and races
x86:
- fix missing locking related to KVM_CAP_MOVE_ENC_CONTEXT_FROM
- warn on creating a new page table that is the child of an invalid one,
and limit damage before it's too late
- disable use of INVLPGA when NPT is enabled, because it doesn't seem
to flush TLBs correctly
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull vkm fixes from Paolo Bonzini:
"s390:
- fix a lot of small bugs and races
x86:
- fix missing locking related to KVM_CAP_MOVE_ENC_CONTEXT_FROM
- warn on creating a new page table that is the child of an invalid
one, and limit damage before it's too late
- disable use of INVLPGA when NPT is enabled, because it doesn't seem
to flush TLBs correctly"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (26 commits)
KVM: x86/mmu: WARN and clear role.invalid when creating a child shadow page
KVM: SVM: Serialize accesses to the owner and mirror list with separate lock
KVM: SVM: make svm_flush_tlb_gva do a full asid flush if NPT enabled
KVM: s390: Fix cleanup in kvm_s390_pv_create_cpu()
KVM: s390: Fix ordering when adding to SCA
KVM: s390: Return -EINTR if a signal is pending while faulting-in
KVM: s390: Free the mmu cache when kvm_arch_vcpu_create() fails
KVM: s390: ucontrol: Add missing locking around gmap_remove_child()
KVM: s390: cmma: Fix dirty tracking when removing memslot
KVM: s390: Fix race in __do_essa()
KVM: s390: Fix leaking of PGM_ADDRESSING to userspace
KVM: s390: ucontrol: Fix sca_clear_ext_call()
KVM: s390: Fix overclearing ESCA in case of error
KVM: s390: Fix kvm_s390_vcpu_unsetup_cmma()
KVM: s390: Do not free SCA if it was not allocated
KVM: s390: Fix unlikely NULL gmap dereference
s390/vfio_ccw: Implement a crw lock
s390/vfio_ccw: Selectively expand io_mutex
s390/vfio_ccw: Move cp cleanup out of not operational
s390/vfio_ccw: Cancel existing workqueues
...
Explicitly clear role.invalid when deriving a child shadow page's role from
its parent to harden against bugs elsewhere in KVM, as violating KVM's
invariant that invalid pages are NOT on the list of active MMU pages leads
to use-after-free due to __kvm_mmu_prepare_zap_page() using list_add()
instead of list_move() when processing an invalid shadow page, i.e. makes a
bad situation far worse.
Yell loudly if the parent is invalid, as it means KVM has missed a validity
check, i.e. KVM is attempting to map memory using an invalid/obsolete root,
but continue on as the child is otherwise still a valid shadow page.
==================================================================
BUG: KASAN: slab-use-after-free in __kvm_mmu_get_shadow_page+0x1817/0x1860 [kvm]
Write of size 8 at addr ff11000153dd1368 by task repro/853
CPU: 1 UID: 1000 PID: 853 Comm: repro Not tainted 7.2.0-rc2-3aec122bdcaf-next-vm #5 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
<TASK>
dump_stack_lvl+0x4b/0x70
print_report+0x153/0x49c
kasan_report+0xbc/0xf0
__kvm_mmu_get_shadow_page+0x1817/0x1860 [kvm]
mmu_alloc_root+0x141/0x320 [kvm]
kvm_mmu_load+0x612/0x20f0 [kvm]
kvm_arch_vcpu_ioctl_run+0x3dd5/0x6150 [kvm]
kvm_vcpu_ioctl+0x5e4/0x10d0 [kvm]
__x64_sys_ioctl+0x131/0x1b0
do_syscall_64+0x67/0x5f0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
Allocated by task 853:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
__kasan_slab_alloc+0x5f/0x70
kmem_cache_alloc_noprof+0xfe/0x2e0
__kvm_mmu_topup_memory_cache+0x135/0x530 [kvm]
paging64_page_fault+0x318/0x1e30 [kvm]
kvm_mmu_do_page_fault+0x21d/0x630 [kvm]
kvm_mmu_page_fault+0x18c/0x17b0 [kvm]
kvm_arch_vcpu_ioctl_run+0x1f35/0x6150 [kvm]
kvm_vcpu_ioctl+0x5e4/0x10d0 [kvm]
__x64_sys_ioctl+0x131/0x1b0
do_syscall_64+0x67/0x5f0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Freed by task 853:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x43/0x70
kmem_cache_free+0xe2/0x400
kvm_mmu_commit_zap_page.part.0+0x1e2/0x310 [kvm]
kvm_mmu_free_roots+0x283/0x560 [kvm]
kvm_arch_vcpu_ioctl_run+0x33c8/0x6150 [kvm]
kvm_vcpu_ioctl+0x5e4/0x10d0 [kvm]
__x64_sys_ioctl+0x131/0x1b0
do_syscall_64+0x67/0x5f0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Fixes: a770f6f28b ("KVM: MMU: Inherit a shadow page's guest level count from vcpu setup")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Interaction between KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM and
KVM_CAP_VM_COPY_ENC_CONTEXT_FROM can cause two separate issues:
- in sev_migrate_from(), when the destination KVM is a mirror, the mirror
entry is moved from the source's list to the owner's mirror_vms list,
without holding the owner's lock unlike other writers of the owner's
mirror list (sev_vm_copy_enc_context_from(), sev_vm_destroy()).
A concurrent COPY or destroy can race with sev_migrate_from() and
corrupt the list.
- In sev_vm_destroy(), the *owner* is still active and could receive
concurrently a KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM that causes
sev->enc_context_owner to change. In this case the incorrect VM
receives kvm_put_kvm().
The second issue needs particular care because the owner could disappear
altogether (even though the race window is impossibly small) between
reading it and locking it. There is thus no way to perform the checks
under the owner lock without putting struct kvm under SLAB_TYPESAFE_BY_RCU
(which would allow kvm_get_kvm_safe() under RCU critical section).
It is much simpler to just use a global lock, since the critical
sections are so small and the new lock is always a leaf lock.
Fixes: b2125513df ("KVM: SEV: Allow SEV intra-host migration of VM with mirrors")
Cc: stable@vger.kernel.org
Reported-by: Shen Yongchao <grayhat@foxmail.com>
Link: https://lore.kernel.org/kvm/tencent_625C0F42824E542C72B34733392AF2C49709@qq.com/
Link: https://lore.kernel.org/kvm/tencent_DDC4E4352EC91CAC05A9A8F4E55E8C96730A@qq.com/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Red Hat is seeing multiple reports of Windows memory corruptions
(and consequent BSODs) with hv-tlbflush=on, on AMD processors only.
The crashes, while extremely rare, happen even with a stock configuration,
but with Driver Verifier enabled they can be detected after approximately
200 VM hours. In particular, Alexander Lougovski measured the following:
- on AMD Turin, 15 crashes in 3300 VM hours
- on AMD Milan, 2 crashes in 500 VM hours (there are fewer hours
here due to the host being smaller)
- on Intel Sapphire Rapids, 0 crashes in 8000 VM hours
- on AMD Turin with full TLB flush (not exactly this patch but
similar), no crashes in ~2 weeks of run time which should also
be ~7000 VM hours
For Turin, the microcode version was 0x0b002162, which (assuming
this is the same issue) should not be affected by the problem listed in
https://knowledge.broadcom.com/external/article/419026/bsod-on-virtual-machines-running-on-amd.html;
on the other hand that problem should not apply to earlier processors.
AMD has not provided any information or analysis yet, and when we asked
we didn't know yet that it reproduced on Milan as well.
As to the workload, Alexander threw more or less everything at the same
time at the VM:
- a full Windows Defender scan every 30 minutes
- a disk I/O job
- a loop doing repeated mmap of system files (mostly to hope that
it triggers some consistency check in the Windows memory manager)
- SQL Express 2022 + StressDB (1.6M rows), with the host doing queries
(75% write/25% read) via sqlcmd
Driver Verifier is able to detect BSODs more or less at the same time as
the pages are freed. They mostly happen in the Windows Defender filter
driver, but occasionally also in the networking stack (e.g., afd.sys)
or elsewhere in the filesystem stack (e.g., fltmgr.sys).
The flush is issued from kvm_hv_vcpu_flush_tlb(), which receives the
cross-CPU requests from the Hyper-V TLB flush hypercalls via a kfifo
and is invoked by the KVM_REQ_HV_TLB_FLUSH request. The mechanism is
the same for both Intel and AMD, and the handler for both vendors is
a simple INVVPID(ADDR)/INVLPGA instruction.
Because the request is handled on the destination CPU, there is a question
of what happens if the VM is migrated across physical CPUs. In that case,
the INVLPGA instruction would use a stale svm->vmcb->control.asid; but
if anything that might do an *unnecessary* flush (on an asid that's being
used for another VM) and then pre_svm_run() would force a full TLB rebuild.
So, for lack of better ideas, this patch forces a full ASID bump in
svm_flush_tlb_gva(). To avoid paying the price on Intel and also to
avoid unnecessary loops on AMD, the flush_tlb_gva op now returns whether
it did a full flush or not; kvm_hv_vcpu_flush_tlb() takes note and exits
its loops immediately. While there is an obvious performance impact,
about half of the benefit from Hyper-V tlbflush is preserved (10% vs. 20%
on the SQL Server workload).
kvm_mmu_invalidate_addr() is the only other caller of the flush_tlb_gva op.
The change would have a performance impact on every intercepted INVLPG and,
for nested SVM, on every L1 INVLPGA. For INVLPGA specifically, this covers
the same suspected issue but for nested hypervisors, so it is correct to
apply the workaround; for INVLPG on shadow paging, instead, the impact
would be stronger and, due to lack of data, for now the use of INVLPGA is
left in place in svm_flush_tlb_gva().
Analyzed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Analyzed-by: Alexander Lougovski <alougovs@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
sequence used in the SRSO mitigation and still poisoning the RSB.
Do that by emulating the saferet sequence and thus avoiding executing
a RET instruction.
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Merge tag 'x86_bugs_saferet' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
- Add a mitigation for the attack vector of interrupting the saferet
sequence used in the SRSO mitigation and still poisoning the RSB.
Do that by emulating the saferet sequence and thus avoiding executing
a RET instruction.
* tag 'x86_bugs_saferet' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/bugs: Make Safe-RET robust against interrupt injection
I hit the following on one of my machines:
mce: CPU0 BANK15 CMCI inherited storm
------------[ cut here ]------------
ODEBUG: assert_init not available (active state 0) object: (____ptrval____) object type: timer_list hint: 0x0
WARNING: lib/debugobjects.c:632 at debug_object_assert_init+0x178/0x230, CPU#0: swapper/0/0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc5 #3 PREEMPTLAZY
RIP: 0010:debug_object_assert_init+0x18f/0x230
Call Trace:
<TASK>
__mod_timer
mce_timer_kick
cmci_discover
intel_init_cmci
mce_intel_feature_init
mcheck_cpu_init
identify_cpu
identify_boot_cpu
arch_cpu_finalize_init
start_kernel
A second splat follows right after, from timer_setup() finding that same
timer already queued:
ODEBUG: init active (active state 0) object: (____ptrval____) object type: timer_list hint: stub_timer+0x0/0x10
This is happening because CMCI storm detection is trying to modify the timer
before latter was properly set up.
Set up the timer first. __mcheck_cpu_setup_timer() only calls timer_setup(),
and depends on neither the generic nor the vendor init.
[ bp: Massage commit message. ]
Fixes: 1f68ce2a02 ("x86/mce: Handle Intel threshold interrupt storms")
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260803-mce_timer_init-v1-1-9539db424330@debian.org
- Fix the boot-time memcmp() asm implementation's constraints
and optimization properties (Mauricio Faria de Oliveira)
- Move the 0xd0...0xd7 AMD Zen5 model range from the Zen6
range where it mistakenly ended up (Pratik Vishwakarma)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-08-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull misc x86 fixes from Ingo Molnar:
- Fix the boot-time memcmp() asm implementation's constraints
and optimization properties (Mauricio Faria de Oliveira)
- Move the 0xd0...0xd7 AMD Zen5 model range from the Zen6
range where it mistakenly ended up (Pratik Vishwakarma)
* tag 'x86-urgent-2026-08-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/CPU/AMD: Carve out a Zen5 models range
x86/boot: Add volatile, clobbers and zero-length test in memcmp()
Always update x2APIC MSR intercepts for L1 when AVIC is deactivated, even
if L2 is active and KVM is using a separate MSR bitmap to run L2. If AVIC
is fully enabled prior to running L2, and is then inhibited while L2 is
active (for a VM-scoped inhibit), then KVM will run L1 with AVIC disabled,
but with x2APIC MSR intercepts disabled, i.e. will allow L1 to read most of
the host's APIC state, send arbitrary interrupts, change task priority, and
ultimately trivially DoS the host.
E.g. sending a self-IPI in L1 on HYPERV_REENLIGHTENMENT_VECTOR, 0xee, with
CONFIG_HYPERV=n in the host kernel as a "safe" PoC, yields:
Spurious interrupt (vector 0xee) on CPU#425. Acked
And hacking KVM to abuse kvm_set_posted_intr_wakeup_handler() to register a
handler and WARN on POSTED_INTR_WAKEUP_VECTOR yields:
------------[ cut here ]------------
WARNING: arch/x86/kvm/svm/svm.c:5594 at pi_wakeup_handler+0x9/0x10 [kvm_amd], CPU#156: nested_x2apic_t/316940
CPU: 156 UID: 0 PID: 316940 Comm: nested_x2apic_t Tainted: G S U
Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER
Hardware name: Google Astoria-Turin/astoria, BIOS 0.20260209.0-0 02/09/2026
RIP: 0010:pi_wakeup_handler+0x9/0x10 [kvm_amd]
Call Trace:
<IRQ>
sysvec_kvm_posted_intr_wakeup_ipi+0x64/0x80
</IRQ>
<TASK>
asm_sysvec_kvm_posted_intr_wakeup_ipi+0x1a/0x20
RIP: 0010:vcpu_run+0x1430/0x1e40 [kvm]
kvm_arch_vcpu_ioctl_run+0x2c1/0x600 [kvm]
kvm_vcpu_ioctl+0x580/0x6b0 [kvm]
__se_sys_ioctl+0x6d/0xb0
do_syscall_64+0x10a/0x480
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x46ff4b
</TASK>
---[ end trace 0000000000000000 ]---
Fixes: 091abbf578 ("KVM: x86: nSVM: optimize svm_set_x2apic_msr_interception")
Cc: stable@vger.kernel.org
Cc: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20260729213558.639074-1-pbonzini@redhat.com/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Family 0x1a, model 0xd0..0xd7 belongs to the Zen5 generation. Carve it
out from the larger, Zen6 range where former doesn't belong.
[ bp: Rewrite commit message, add tags. ]
Fixes: b5f53e6d3d ("x86/CPU/AMD: Add more Zen6 models")
Signed-off-by: Pratik Vishwakarma <Pratik.Vishwakarma@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260729055459.15904-1-Pratik.Vishwakarma@amd.com
Add the volatile qualifier and clobbers parameter to prevent bugs with
instruction reordering and optimization.
Also add TEST for the zero-length case to set ZF, as, if the count register
is zero, the REPE prefix does not run the CMPSB instruction, leaving the ZF
flag undetermined.
[ bp: Add a comment about the len==0 case. ]
Fixes: 62bd0337d0 ("Top header file for new x86 setup code")
Closes: https://sashiko.dev/#/patchset/20260701-pvh-kasan-inline-v6-0-ba99045dfa9f%40igalia.com
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Mauricio Faria de Oliveira <mfo@igalia.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/all/20260721-pvh-kasan-inline-v7-2-38979a50cef0@igalia.com
mmu_try_to_unsync_pages() skips the shadow-page lookup when the
supplied memslot allows a hugepage, because a shadow page would disallow
hugepages. But hugepage metadata is per-address-space while shadow pages
are shared across all address spaces. With SMM, the other address space
can therefore have a shadow page even when the supplied memslot allows a
hugepage.
Check the corresponding memslot in the other address space before
taking the fast path. Skip the shadow-page lookup only when all address
spaces allow a hugepage.
Fixes: b3ae3ceb55 ("KVM: x86/mmu: KVM: x86/mmu: Skip unsync when large pages are allowed")
Assisted-by: Codex:GPT-5
Signed-off-by: Jinu Kim <kimjw04271234@gmail.com>
[invert direction of the conditional. - Paolo]
Message-ID: <20260721103512.2136240-3-kimjw04271234@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_gfn_is_write_tracked() checks only the supplied memslot, but page
tracking is per-address-space and shadow pages are shared across all
address spaces. With SMM, a GFN can therefore be write-tracked in one
address space and appear untracked through the other.
Check the supplied slot first, then the slot for the other address space.
This ensures all callers honor write tracking regardless of the active
address space. In particular, it prevents mmu_try_to_unsync_pages() from
marking an upper-level shadow page unsync and eventually triggering the
BUG in pte_list_remove().
Fixes: 699023e239 ("KVM: x86: add SMM to the MMU role, support SMRAM address space")
Assisted-by: Codex:GPT-5
Signed-off-by: Jinu Kim <kimjw04271234@gmail.com>
Message-ID: <20260721103512.2136240-2-kimjw04271234@gmail.com>
[invert direction of the conditional. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cancel (and flush) the I/O APIC's delayed EOI handling work during the
"pre VM destroy" phase, before vCPUs are destroyed, as processing the EOI
broadcast will inject another IRQ if the line is asserted, i.e. will try
to deliver an IRQ to the target vCPU(s). Canceling the work after vCPUs
are destroyed leads to UAF if the delayed work is processed after vCPUs are
destroyed.
BUG: KASAN: slab-use-after-free in __kvm_irq_delivery_to_apic_fast+0x9bf/0xa20 arch/x86/kvm/lapic.c:1250
Read of size 8 at addr ffff8880499abea0 by task kworker/1:2/1218
CPU: 1 UID: 0 PID: 1218 Comm: kworker/1:2 Not tainted 7.1.0-rc7 #5 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 25.10 PC v2 (i440FX + PIIX, + 10.1 machine, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events kvm_ioapic_eoi_inject_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378
print_report+0x139/0x4ad mm/kasan/report.c:482
kasan_report+0xe4/0x1d0 mm/kasan/report.c:595
__kvm_irq_delivery_to_apic_fast+0x9bf/0xa20 arch/x86/kvm/lapic.c:1250
__kvm_irq_delivery_to_apic+0xd8/0xbf0 arch/x86/kvm/lapic.c:1345
kvm_irq_delivery_to_apic arch/x86/kvm/lapic.h:129
ioapic_service+0x308/0x590 arch/x86/kvm/ioapic.c:492
kvm_ioapic_eoi_inject_work+0x13c/0x190 arch/x86/kvm/ioapic.c:532
process_one_work+0xa59/0x19a0 kernel/workqueue.c:3314
process_scheduled_works kernel/workqueue.c:3397
worker_thread+0x5eb/0xe50 kernel/workqueue.c:3478
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Note, the VM is unreachable once kvm_destroy_vm() starts, and scheduling
new work via kvm_ioapic_send_eoi() can only be done via KVM_RUN, i.e.
requires a live vCPU.
Alternatively, KVM could simply destroy the I/O APIC during the "pre" phase
of VM destruction, but that gets more than a bit sketchy as KVM expects the
I/O APIC to exist if ioapic_in_kernel() is true, and nested virtualization
in particular has a bad habit of touching VM-scope state during vCPU
destruction. E.g. attempting to free the PIC during the pre phase would
lead to a NULL pointer dereference in kvm_cpu_has_extint(), and it's not
hard to imagine the I/O APIC having a similar flaw.
Fixes: 17bcd71442 ("KVM: x86: Free vCPUs before freeing VM state")
Reported-by: <zdi-disclosures@trendmicro.com>
Reported-by: Zhong Wang <wangzhong.c0ss4ck@bytedance.com>
Reported-by: Xuanqing Shi <shixuanqing.11@bytedance.com>
Cc: stable@vger.kernel.org
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260727171718.543491-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
VMCLEAR/VMREAD/VMWRITE/VMPTRLD access the internal VMCS cache, which
is not visible to the compiler; without a memory clobber, the compiler
can reorder them in troublesome ways because "asm volatile" and "asm goto"
only protect against removal of the asm. For example, placing a VMWRITE
before the corresponding VMCS pointer is loaded can lead to corruption.
While none of this has been observed, it is better to prevent than cure.
Likewise, INVEPT and INVVPID access the TLB and, even though in their
case the effect is only visible to the next VMLAUNCH/VMRESUME, it is
technically correct to add the clobber there too. So avoid any urge to
special case them, and simply hardcode "memory" into the clobber list
of vmx_asm1() and vmx_asm2(). __vmcs_readl() open-codes its own asm,
so add the clobber there as well.
Link: https://lore.kernel.org/kvm/CABgObfbL3t21yVeSwiLSjjOUER+rTYDPHYAH9YU4TWGRjx6XHg@mail.gmail.com/
Cc: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
a bit more widely, because newer versions of LLVM started
optimizing it a bit better and introduced run-time relocations
in PIE code. (Nathan Chancellor)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-07-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fix from Ingo Molnar:
- Disable jump/lookup tables in the x86 boot decompressor code
a bit more widely, because newer versions of LLVM started
optimizing it a bit better and introduced run-time relocations
in PIE code (Nathan Chancellor)
* tag 'x86-urgent-2026-07-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot/compressed: Disable jump tables
An attacker injecting interrupts while the Safe-RET mitigation executes
on machines affected by SRSO can neutralize the safe return sequence,
potentially leading to data leakage through speculative execution.
Fixup register state as if the Safe-RET sequence executed successfully
by "emulating" it, in a manner of speaking, and avoid executing a RET
instruction after returning from the interrupt.
Co-developed-by: David Kaplan <David.Kaplan@amd.com>
Signed-off-by: David Kaplan <David.Kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
After a recent upstream LLVM change to start generating jump and lookup
tables in switch statements in more instances [1], linking the
compressed x86 boot image when CONFIG_KERNEL_ZSTD is enabled fails with:
ld.lld: error: Unexpected run-time relocations (.rela) detected!
Dumping the relocations in misc.o, which is the only file influenced by
CONFIG_KERNEL_ZSTD in the decompressor, shows dynamic relocations to
some string constants, which correspond to the string literals in the
switch statement in handle_zstd_error():
Relocation section '.rela.data.rel.ro' at offset 0x277b0 contains 31 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 73a
0000000000000008 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
0000000000000010 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
0000000000000018 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
...
This optimization is problematic for the decompressor environment, as it
is built as -fPIE without any explicit absolute references (as described
at the top of misc.c) while not applying any dynamic relocations, hence
the linker assertion. To opt out of this optimization, which is of
little value in this special early boot code, and to mirror the other
x86 startup code in arch/x86/boot/startup, disable jump tables in the
decompressor.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: fa02a6ed66 [1]
Link: https://patch.msgid.link/20260722-x86-boot-compressed-disable-jt-clang-v2-1-7373d38482fb@kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/2165
- Avoid redundant allocations when allocating IMSIC page tables
- Apply SBI FWFT LOCK flag only on successful set
- Bound SBI PMU counter mask scan to BITS_PER_LONG, since on RV32
the PMU SBI start/stop helper can only access 32 PMU counters.
- Skip TLB flush when G-stage PTE becomes valid if the Svvptc
extension is available.
- Always show Zicbo[m|z|p] block sizes in ONE_REG
- Inject instruction access fault on unmapped guest fetch
- Use raw spinlock for irqs_pending and irqs_pending_mask
- Fix Spectre-v1 in vector register access via ONE_REG
x86:
- Fixes to SEV selftests.
- Once free_nested() did a VMCLEAR of shadow VMCS, there's no need to VMCLEAR it
again if the kernel is preempted and thread migration happens
- Preserve nested TDP shadow page tables if they are used as roots, instead of
clearing them unnecessarily
- Fix use of stale data if out-of-memory happens after vendor module reload
- Check for invalid/obsolete root *after* making MMU pages available, because
the latter can make a page invalid
- Only reset TSC Deadline Timer in apic_timer_expired on KVM_RUN
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"RISC-V:
- Avoid redundant allocations when allocating IMSIC page tables
- Apply SBI FWFT LOCK flag only on successful set
- Bound SBI PMU counter mask scan to BITS_PER_LONG, since on RV32 the
PMU SBI start/stop helper can only access 32 PMU counters.
- Skip TLB flush when G-stage PTE becomes valid if the Svvptc
extension is available.
- Always show Zicbo[m|z|p] block sizes in ONE_REG
- Inject instruction access fault on unmapped guest fetch
- Use raw spinlock for irqs_pending and irqs_pending_mask
- Fix Spectre-v1 in vector register access via ONE_REG
x86:
- Fixes to SEV selftests
- Once free_nested() did a VMCLEAR of shadow VMCS, there's no need to
VMCLEAR it again if the kernel is preempted and thread migration
happens
- Preserve nested TDP shadow page tables if they are used as roots,
instead of clearing them unnecessarily
- Fix use of stale data if out-of-memory happens after vendor module
reload
- Check for invalid/obsolete root *after* making MMU pages available,
because the latter can make a page invalid
- Only reset TSC Deadline Timer in apic_timer_expired on KVM_RUN"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: x86: Only reset TSC Deadline Timer in apic_timer_expired on KVM_RUN
KVM: selftests: sev_init2_tests: Derive SEV availability from KVM
KVM: selftests: sev_smoke_test: Only run VM types the host offers
KVM: x86/mmu: Fix use-after-free on vendor module reload
KVM: x86/mmu: Preserve nested TDP shadow page tables if they are used as roots
KVM: x86: Check for invalid/obsolete root *after* making MMU pages available
KVM: nVMX: Hide shadow VMCS right after VMCLEAR
KVM: riscv: Fix Spectre-v1 in vector register access
RISC-V: KVM: Serialize virtual interrupt pending state updates
RISC-V: KVM: Inject instruction access fault on unmapped guest fetch
RISC-V: KVM: Zicbo[m|z|p] block sizes should be always present in ONE_REG
riscv: kvm: Skip TLB flush when G-stage PTE becomes valid with Svvptc
KVM: riscv: PMU: Bound counter mask scan to BITS_PER_LONG
KVM: riscv: SBI FWFT: Apply LOCK flag only on successful set
RISC-V: KVM: Avoid redundant page-table allocations in ioremap topup
On Intel platforms with a VMX preemption timer and APICv, if a VMM
calls KVM_GET_LAPIC before KVM_GET_MSRS to save the vCPU state, it is
possible to lose a pending timer interrupt.
If the thread running these ioctls is migrated to another core after
calling KVM_GET_LAPIC but before KVM_GET_MSRS and the guest is using
their LAPIC timer in TSC-deadline mode, not only does the save LAPIC
state not carry the pending interrupt, the TSCDEADLINE MSR will be
zeroed.
After migration across CPUs, KVM_GET_MSRS calls vcpu_load, posting the
interrupt and clearing the MSR:
vcpu_load() ->
kvm_arch_vcpu_load() ->
kvm_lapic_restart_hv_timer() ->
start_hv_timer() ->
apic_timer_expired() ->
kvm_apic_inject_pending_timer_irqs()
. post interrupt into the LAPIC state
. clear IA32_TSCDEADLINE
The saved LAPIC state will be missing the pending interrupt and the saved
MSR will be zero. Oops.
Fix by only posting an interrupt when we're attempting to enter the guest
(vcpu->wants_to_run == true), not for vcpu_load from other paths.
Assisted-by: gemini:gemini-3.1-pro-preview
Debugged-by: David Matlack <dmatlack@google.com>
Debugged-by: Sean Christopherson <seanjc@google.com>
Debugged-by: Jim Mattson <jmattson@google.com>
Debugged-by: James Houghton <jthoughton@google.com>
Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org>
Message-ID: <20260715234234.15382-2-venkateshs@chromium.org>
Reviewed-by: James Houghton <jthoughton@google.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Cc: stable@vger.kernel.org
Fixes: ae95f566b3 ("KVM: X86: TSCDEADLINE MSR emulation fastpath", 2020-05-15)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
mmu_destroy_caches() destroys pte_list_desc_cache and
mmu_page_header_cache, but leaves both pointers unchanged. The pointers
live in kvm.ko, and therefore survive when a vendor module is unloaded
while kvm.ko remains loaded.
If creation of pte_list_desc_cache fails during a subsequent vendor
module load, its assignment sets pte_list_desc_cache to NULL and the
error path calls mmu_destroy_caches(). mmu_page_header_cache still
points to the cache destroyed during the preceding vendor module
unload. Passing that stale pointer to kmem_cache_destroy() causes a
slab use-after-free.
Reproduce the issue on a v7.1.3 kernel with CONFIG_KASAN=y,
CONFIG_KASAN_GENERIC=y, CONFIG_KVM=m, and CONFIG_KVM_INTEL=m. A
one-shot test hook forces pte_list_desc_cache to NULL on the second
invocation of kvm_mmu_vendor_module_init():
1. Load kvm.ko and kvm-intel.ko, creating both caches.
2. Unload only kvm_intel, leaving kvm.ko loaded.
3. Reload kvm_intel and force initialization through the -ENOMEM path.
KASAN reports:
BUG: KASAN: slab-use-after-free in
kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]
...
kmem_cache_destroy+0x21/0x1d0
kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]
...
Allocated by task 16817:
__kmem_cache_create_args+0x12c/0x3b0
__kmem_cache_create.constprop.0+0xb6/0xf0 [kvm]
kvm_mmu_vendor_module_init+0x13b/0x170 [kvm]
...
Freed by task 16820:
kmem_cache_destroy+0x117/0x1d0
kvm_mmu_vendor_module_exit+0x21/0x30 [kvm]
Clear both pointers immediately after destroying their caches so that
the stored state reflects the caches' lifetime and repeated cleanup is
safe.
With the fix applied, the same injected vendor module reload fails with
-ENOMEM as expected and produces no KASAN report.
Fixes: cb498ea2ce ("KVM: Portability: Combine kvm_init and kvm_init_x86")
Cc: stable@vger.kernel.org
Signed-off-by: Phil Rosenthal <phil@phil.gs>
Message-ID: <20260718-kvm-mmu-cache-uaf-v3-1-e103b93c74e1@phil.gs>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_mmu_zap_oldest_mmu_pages() excludes a shadow page whose root_count
is non-zero from top-level reclaim, because such a page cannot be
freed. The path in mmu_page_zap_pte() that recursively zaps a parentless
nested TDP child has no such check. As a result, a shadow page can
be zapped even if the page itself can't be freed; as the comment in
kvm_mmu_zap_oldest_mmu_pages() notes, zapping it will just force vCPUs
to rebuild the page.
As in top-level reclaim, do not recursively prepare zapping of a
nested TDP child whose root_count is non-zero.
Fixes: 2de4085ccc ("KVM: x86/MMU: Recursively zap nested TDP SPs when zapping last/only parent")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Check for a "stale" page fault, i.e. for an invalid and/or obsolete root,
after making MMU pages available for the shadow MMU. If reclaiming shadow
pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to
map memory into an invalid root. On its own, populating an invalid root is
"fine", but because child shadow pages inherit their parent's role, any
children created during the map/fetch will be created as invalid pages,
thus violating KVM's invariant that invalid pages are never on the list of
active MMU pages.
Note, the underlying flaw has existed since KVM first started tracking
invalid roots in 2008 (commit 2e53d63acb, "KVM: MMU: ignore zapped root
pagetables"), but the true badness only came along in 2020 (Linux 5.9)
with the invariant that invalid shadow pages can't be on the list of
active pages.
Note #2, inheriting role.invalid when creating child shadow pages is also
far from ideal; that flaw will be addressed separately.
Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Fixes: f95eec9bed ("KVM: x86/mmu: Don't put invalid SPs back on the list of active pages")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
free_nested() frees the shadow VMCS while vmcs01 still points to it. But
because it is asynchronous with respect to loaded_vmcs_clear(), the vCPU
might migrate before the pointer is cleared and __loaded_vmcs_clear()
may then execute VMCLEAR.
The VMCS needs to stay attached until its explicit VMCLEAR completes, but
then it can be hidden and the page safely freed.
Fixes: 355f4fb140 ("kvm: nVMX: VMCLEAR an active shadow VMCS after last use")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Reject too long acpi_rsdp= boot parameter values
(Thorsten Blum)
- Validate console=uart8250 baud rate to fix early boot hang
(Thorsten Blum)
- Remove dead Makefile rule (Ethan Nelson-Moore)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-07-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Ingo Molnar:
- Reject too long acpi_rsdp= boot parameter values (Thorsten Blum)
- Validate console=uart8250 baud rate to fix early boot hang (Thorsten
Blum)
- Remove dead Makefile rule (Ethan Nelson-Moore)
* tag 'x86-urgent-2026-07-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot: Validate console=uart8250 baud rate to fix early boot hang
x86/boot: Reject too long acpi_rsdp= values
x86/cpu: Remove Makefile rule for removed UMC CPU support
If a vCPU stays scheduled out (or blocked) while the last pCPU it ran
on goes through a hotplug cycle (online->offline->online), and the vCPU
then resumes execution on the same pCPU, then it is possible for it to
run with an ASID that has now been assigned to a different vCPU,
resulting in stale TLB translations being used.
svm_enable_virtualization_cpu() resets asid_generation to 1 and sets
next_asid to max_asid + 1 on every CPU online event, including hotplug
cycles. Because next_asid starts beyond the pool boundary, the first
call to new_asid() after an online event always wraps the pool,
incrementing asid_generation to 2 and assigning ASIDs starting from
min_asid.
Consider two vCPUs from different VMs, vCPU-A pinned to CPU-X holding
asid_generation=2 and ASID=N from before the hotplug event:
1. CPU-X goes offline and back online: asid_generation resets to 1,
next_asid = max_asid + 1.
2. One or more vCPUs migrate to CPU-X and call new_asid(), wrapping
the pool and consuming ASIDs starting from min_asid. Eventually
vCPU-B from a different VM is assigned asid_generation=2, ASID=N
— the same ASID that vCPU-A held before the hotplug.
3. vCPU-A enters pre_svm_run() on CPU-X: current_vmcb->cpu is
unchanged so the migration branch is skipped. Its saved
asid_generation=2 matches sd->asid_generation=2, so the generation
check silently passes and vCPU-A continues running with ASID=N —
the same ASID just freshly assigned to vCPU-B.
Both vCPUs from different VMs now run on CPU-X with the same ASID,
causing them to share NPT TLB entries and producing stale translations.
The collision manifests as a KVM internal error (Suberror: 1, emulation
failure). The NPT page fault reports a faulting GPA far outside the
VM's physical memory range — a sign of stale TLB translations being
used. KVM falls back to instruction emulation, which fails on
FPU/XSave instructions (XRSTOR, STMXCSR) that the emulator does not
implement.
Fix this by incrementing asid_generation instead of resetting it to 1
in svm_enable_virtualization_cpu(). On module load, asid_generation
starts at 0 (memset) and the increment produces 1, identical to the
old behaviour. On subsequent hotplug cycles the generation advances
beyond any value a vCPU previously observed on this CPU, so the
generation check in pre_svm_run() reliably forces new_asid() on every
vCPU after every hotplug cycle.
Fixes: 774c47f1d7 ("[PATCH] KVM: cpu hotplug support")
Reported-by: Chandrakanth Silveru <Chandrakanth.Silveru@amd.com>
Tested-by: Srikanth Aithal <Srikanth.Aithal@amd.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Message-ID: <20260715063506.672432-1-nikunj@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Put all vmcs12 pages if KVM synthesizes a nested VM-Exit due to invalid
guest while emulating VMLAUNCH or VMRESUME. The invalid guest state path
doesn't use nested_vmx_vmexit() as that API is intended to be used if and
only if L2 is active, and the open coded equivalent neglects to put the
vmcs12 pages. Failure to put the vmcs12 pages leaks any pinned pages
(and/or mappings) if L1 retries VMLAUNCH/VMRESUME.
Note, the !from_vmenter scenario doesn't suffer the same problem, as
vmx_get_nested_state_pages() only gets/pins/maps the vmcs12 pages if L2 is
active, i.e. if a "full" VM-Exit is guaranteed before KVM will retry
getting vmcs12 pages.
Fixes: 96c66e87de ("KVM/nVMX: Use kvm_vcpu_map when mapping the virtual APIC page")
Fixes: 3278e04925 ("KVM/nVMX: Use kvm_vcpu_map when mapping the posted interrupt descriptor table")
Fixes: fe1911aa44 ("KVM: nVMX: Use kvm_vcpu_map() to get/pin vmcs12's APIC-access page")
Reported-by: Minh Nguyen <minhnguyen.080505@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Fix a bug where KVM will trigger a UAF if updating IOMMU IRTEs fails when
registering an IRQ-bypass producer.
- Ignore pending PV EOI instead of BUG()ing the host if the feature was
disabled by the guest.
- Fix nVMX bugs where KVM would run L1 with an L1-controlled CR3 after a
failed "late" consistency check when KVM is NOT using EPT.
- Disallow intra-host migration/mirroring of SNP VMs as KVM doesn't yet
support moving/mirroring SNP state.
- Fix a TOCTOU bug in KVM's handling of the "trusted" CPUID for TDX guests.
- Fix a NULL pointer deref in trace_kvm_inj_exception() where a change to the
core infrastructure missed KVM's unique (ab)use of __print_symbolic().
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Merge tag 'kvm-x86-fixes-7.2-rc4' of https://github.com/kvm-x86/linux into HEAD
KVM x86 fixes for 7.2-rcN
- Fix a bug where KVM will trigger a UAF if updating IOMMU IRTEs fails when
registering an IRQ-bypass producer.
- Ignore pending PV EOI instead of BUG()ing the host if the feature was
disabled by the guest.
- Fix nVMX bugs where KVM would run L1 with an L1-controlled CR3 after a
failed "late" consistency check when KVM is NOT using EPT.
- Disallow intra-host migration/mirroring of SNP VMs as KVM doesn't yet
support moving/mirroring SNP state.
- Fix a TOCTOU bug in KVM's handling of the "trusted" CPUID for TDX guests.
- Fix a NULL pointer deref in trace_kvm_inj_exception() where a change to the
core infrastructure missed KVM's unique (ab)use of __print_symbolic().
When the baud rate is empty, 0, invalid, or overflows to 0 when stored
as an int, the system will hang during early boot because of a division
by zero in early_serial_init().
Fall back to DEFAULT_BAUD when the resulting baud rate is 0 to prevent
an early system hang.
Fixes: ce0aa5dd20 ("x86, setup: Make the setup code also accept console=uart8250")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260713194924.126472-3-thorsten.blum@linux.dev
The trace_kvm_inj_exception tracepoint takes as arguments the exception
vector, whether the exception has an error code (and subsequently, the
error code), and whether it is being reinjected. Because '0' is a valid
error code, KVM uses __print_symbolic() to format the error code as a
string to avoid printing the error code entirely if the exception doesn't
have an error code (see commit 21d4c575eb ("KVM: x86: Print error code
in exception injection tracepoint iff valid").
KVM's abuse of __print_symbolic() was all fine and dandy, until commit
754e38d2d1 ("tracing: Use explicit array size instead of sentinel
elements in symbol printing") reworked the printing to avoid terminating
the arrays with NULL/0 values, and missed KVM's clever use of not-quite
empty array of symbols.
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 [#1] SMP
CPU: 20 UID: 0 PID: 791 Comm: less Not tainted 7.2.0-rc2 #401 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:strlen+0x0/0x20
Call Trace:
<TASK>
trace_seq_puts+0x18/0x80
trace_print_symbols_seq+0x68/0xa0
trace_raw_output_kvm_inj_exception+0x64/0xf0 [kvm]
s_show+0x47/0x110
seq_read_iter+0x2a5/0x4c0
seq_read+0xfd/0x130
vfs_read+0xb6/0x330
? vfs_write+0x2f2/0x3f0
ksys_read+0x61/0xd0
do_syscall_64+0xb7/0x570
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7ff283714862
</TASK>
Simply drop the dummy array entirely, so that __print_symbolic() generates
a truly empty array.
Signed-off-by: Daniel Paziyski <danielpaziyski@gmail.com>
Fixes: 754e38d2d1 ("tracing: Use explicit array size instead of sentinel elements in symbol printing")
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260710134055.16432-1-danielpaziyski@gmail.com
[sean: massage changelog, add splat, add Fixes, cc stable]
Signed-off-by: Sean Christopherson <seanjc@google.com>
cmdline_find_option() returns the full length of the parsed acpi_rsdp=
value. get_cmdline_acpi_rsdp() then silently truncates values which do
not fit in the val[] buffer.
Prevent boot_kstrtoul() from parsing a truncated value and then the
kernel from silently using the wrong RSDP address, see discussion in
Link:.
Issue a warning so that the user is aware that s/he supplied a malformed
value and can get feedback instead of silent crashes.
[ bp: Make commit message more precise. ]
Fixes: 3c98e71b42 ("x86/boot: Add "acpi_rsdp=" early parsing")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20260617130417.36651-4-thorsten.blum@linux.dev
Support for UMC CPUs was removed in
7d328c5de4 ("x86/cpu: Remove CPU_SUP_UMC_32 support"),
but a Makefile rule for the support code remained. Remove it.
Fixes: 7d328c5de4 ("x86/cpu: Remove CPU_SUP_UMC_32 support")
Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ahmed S. Darwish <darwi@linutronix.de>
Link: https://patch.msgid.link/20260610033252.164571-1-enelsonmoore@gmail.com
A user-only branch stack can contain branches that originate from
the kernel. As a result, kernel addresses are exposed to user space
even when PERF_SAMPLE_BRANCH_USER is requested. On AMD processors
supporting X86_FEATURE_BRS (Zen 3 only), perf can still report entries
such as SYSRET/interrupt returns for which the branch-from addresses
are in the kernel.
E.g.
$ perf record -j any,u -c 4000 -e branch-brs -o - -- \
perf bench syscall basic --loop 1000 | \
perf script -i - -F brstack|tr ' ' '\n'| \
grep -E '0x[89a-f][0-9a-f]{15}'
...
0xffffffff810001c4/0x72e2e32955eb/-/-/-/0//-
0xffffffff810001c4/0x72e2d94a9821/-/-/-/0//-
0xffffffff810001c4/0x72e2d94ffa1b/-/-/-/0//-
...
BRS provides no hardware branch filtering, so privilege level
filtering is performed entirely in software. However, amd_brs_match_plm()
only validates the branch-to address against the requested privilege
levels. For branches from the kernel to user space, the branch-from
address is left unchecked and is leaked. Extend the software filter to
also validate the branch-from address, so that any branch record whose
branch-from address is in the kernel is dropped when
PERF_SAMPLE_BRANCH_USER is requested.
Fixes: 8910075d61 ("perf/x86/amd: Enable branch sampling priv level filtering")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://patch.msgid.link/f05931c4f89a146c364bd5dc6b8170b1ac611c65.1783701239.git.sandipan.das@amd.com
Closes: https://lore.kernel.org/all/20260710110235.F3FD81F000E9@smtp.kernel.org/
Reject KVM_TDX_INIT_VM if userspace changes cpuid.nent between the
initial read and the subsequent copy of the initialization data.
tdx_td_init() first reads user_data->cpuid.nent to size the flexible
kvm_tdx_init_vm copy. The copied structure also contains cpuid.nent,
and that field can differ from the value used to size the allocation if
userspace modifies the input concurrently. setup_tdparams_cpuids() later
passes init_vm->cpuid.nent to kvm_find_cpuid_entry2(), which uses it as
the array bound for the copied entries.
Require the copied count to match the value used to size the allocation
so that CPUID parsing cannot access beyond the entries actually copied.
Fixes: 0bd0a4a142 ("KVM: TDX: Replace kmalloc + copy_from_user with memdup_user in tdx_td_init()")
Reported-by: Sashiko:gemini-3.1-pro-preview
Cc: <stable@vger.kernel.org>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20260710035324.3170534-1-binbin.wu@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The intra-host migration/mirroring feature is not fully implemented for
SEV-SNP VMs. The proper migration requires additional SNP-specific
state such as guest_req_mutex, guest_req_buf, and guest_resp_buf to be
transferred or initialized on the destination.
The SNP VM mirroring requires vmsa features to be copied as well otherwise
ASID would be bound to SNP range while VM is detected as a SEV VM.
Reject SNP source VMs in migration/mirroring until proper SNP state
transfer is implemented.
Fixes: 1dfe571c12 ("KVM: SEV: Add initial SEV-SNP support")
Reported-by: Chris Mason <clm@meta.com>
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Atish Patra <atishp@meta.com>
Link: https://patch.msgid.link/20260602-sev_snp_fixes-v3-1-24bfd3ae047c@meta.com
Cc: stable@vger.kernel.org
[sean: let lines poke past 80 chars, tag for stable]
Signed-off-by: Sean Christopherson <seanjc@google.com>
A user-only branch stack can contain branches that originate from
the kernel. As a result, kernel addresses are exposed to user space
even when PERF_SAMPLE_BRANCH_USER is requested. On AMD processors
supporting X86_FEATURE_AMD_LBR_V2, perf can still report SYSRET/ERET
entries for which the branch-from addresses are in the kernel.
E.g.
$ perf record -e cycles -o - -j any,save_type,u -- \
perf bench syscall basic --loop 1000 | \
perf script -i - -F brstack|tr ' ' '\n'| \
grep -E '0x[89a-f][0-9a-f]{15}'
...
0xffffffff81001268/0x717a90a38f1a/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a90a39157/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a90a2c628/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a90a41b60/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a8bef1c30/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
0xffffffff81001268/0x717a8e4d3c90/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH
...
The reason is that the hardware filter only considers the privilege
level applicable to the branch target. Extend software filtering to
also validate the branch-from addresses against br_sel, so that any
branch record whose branch-from address is in the kernel is dropped
when PERF_SAMPLE_BRANCH_USER is requested.
Fixes: f4f925dae7 ("perf/x86/amd/lbr: Add LbrExtV2 hardware branch filter support")
Reported-by: Ian Rogers <irogers@google.com>
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/a898a29725f6b2f30518354cdc2e432db66c43cf.1783680119.git.sandipan.das@amd.com
Add a dedicated field in "struct nested_vmx" to track L1's pre-VM-Enter CR3
instead of using vmcs01.GUEST_CR3, which isn't anywhere near as safe as the
comment purports it to be. E.g. in addition to the warn_on_missed_cc bug
(that was fixed by relocating the consistency check), if getting vmcs12
pages (during actual nested VM-Entry) fails and EPT is disabled (in KVM),
KVM will return control to userspace with vmcs01.GUEST_CR3 holding a guest-
controlled value.
Alternatively, KVM could force a reload of vmcs01.GUEST_CR3 by resetting
the MMU context in the error path, but as above, the safety of the vmcs01
approach is extremely questionable, e.g. it took all of ~4 months for the
code to break.
Fixes: 671ddc700f ("KVM: nVMX: Don't leak L1 MMIO regions to L2")
Cc: stable@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260612145642.452392-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Move the off-by-default consistency check for vmcs12.tpr_threshold vs.
the virtual APIC vTPR into the "normal" controls checks, as waiting until
KVM has loaded some amount of state is unnecessary and actively dangerous.
Specifically, failure to unwind vmcs01.GUEST_CR3 to KVM's value when EPT
is disabled results in KVM running L1 with an L1-controlled CR3, not with
KVM's CR3!
Alternatively, KVM could simply reset the MMU to force a reload of
vmcs01.GUEST_CR3, but the _only_ reason the check was shoved into a "late"
flow was to wait until the vmcs12 pages were retrieved. Rather than build
up more crusty code, simply access vTPR using a regular guest memory access
(performance isn't a concern). To circumvent the restrictions that led to
KVM deferring nested_get_vmcs12_pages(), (a) use a VM-scoped API to read
guest memory so that it always hits non-SMM memslots (for RSM), and (b)
skip the check (since its off-by-default anyways) when the vCPU doesn't
want to run, i.e. when userspace is restoring/stuffing state.
If reading guest memory fails, simply skip the consistency check, as KVM's
de facto ABI is that VMX instruction accesses to non-existent memory get
PCI Bus Error semantics, where reads return 0xFFs. And if vTPR=0xFF, then
the vTPR is guaranteed to be greater than or equal to TPR_THRESHOLD.
Fixes: 1100e4910a ("KVM: nVMX: Add an off-by-default module param to WARN on missed consistency checks")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260612145642.452392-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Nullify irqfd->producer if updating the IRTE for bypass fails, as leaving a
dangling pointer will result in a use-after-free if the irqfd is reachable
through KVM's routing, but the producer is freed separately. E.g. for VFIO
PCI, the producer is embedded in struct "vfio_pci_irq_ctx" and freed when
the vector is disabled, which can happen independent of routing updates.
Fixes: 77e1b8332d ("KVM: x86: Decouple device assignment from IRQ bypass")
Cc: stable@vger.kernel.org
Signed-off-by: leixiang <leixiang@kylinos.cn>
Link: https://patch.msgid.link/1782119051448443.14545.seg@mailgw.kylinos.cn
[sean: drop PPC change, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Branch Sampling (BRS) and Last Branch Record (LBR) are mutually
exclusive hardware features, and users of both are tracked via
cpuc->lbr_users.
When SVM is toggled on a CPU, the host perf events are reprogrammed to
update the HostOnly filter bit (set when virtualization is enabled,
cleared when it is disabled). On PerfMonV2-capable processors, this
reprogramming is performed by calling amd_pmu_enable_all() to rewrite
the event selectors. However, amd_pmu_enable_all() also calls
amd_brs_enable_all(), which enables BRS whenever cpuc->lbr_users > 0.
Having active LBR events satisfies this gating on processors that have
LBR but not BRS. The kernel then tries to set the BRS enable bit in
DebugExtnCfg (MSR 0xc000010f). Since that bit is deprecated on such
hardware, the write results in a #GP:
Call Trace:
<IRQ>
amd_pmu_enable_all+0x1d/0x90
amd_pmu_disable_virt+0x62/0xb0
kvm_arch_disable_virtualization_cpu+0xa/0x40 [kvm]
hardware_disable_nolock+0x1a/0x30 [kvm]
__flush_smp_call_function_queue+0x9b/0x410
__sysvec_call_function+0x18/0xc0
sysvec_call_function+0x69/0x90
</IRQ>
<TASK>
asm_sysvec_call_function+0x16/0x20
RIP: 0010:cpuidle_enter_state+0xc4/0x450
? cpuidle_enter_state+0xb7/0x450
cpuidle_enter+0x29/0x40
cpuidle_idle_call+0xf5/0x160
do_idle+0x7b/0xe0
cpu_startup_entry+0x26/0x30
start_secondary+0x115/0x140
secondary_startup_64_no_verify+0x194/0x19b
</TASK>
Fix this by ensuring that BRS is not enabled from the event selector
reprogramming path even when cpuc->lbr_users > 0.
Fixes: bae19fdd7e ("perf/x86/amd/core: Fix reloading events for SVM")
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/702fa204d574b03d14e3664c7d4b201db048bbfd.1783506528.git.sandipan.das@amd.com
Revert
99cf1fb58e ("x86/virt/sev: Drop WBINVD before setting MSR_AMD64_SYSCFG_SNP_EN").
Section 8.8 of the SNP spec says:
Before invoking SNP_INIT_EX with INIT_RMP set to 1, software must ensure
that no CPUs contain dirty cache lines for the memory containing the RMP.
Cachelines can be moved from cache to cache in a dirty state. The
wbinvd_on_all_cpus() before SNP_INIT_EX flushes the caches for each CPU, but
if the IPIs for WBINVD race with this dirty cacheline movement, it is possible
that they may not get flushed, violating the firmware requirement.
Doing wbinvd_on_all_cpus() before setting SNPEn is safer since the RMP
table is not yet in use.
[ Heroically bisected by Srikanth. ]
[ bp: Massage commit message. ]
Fixes: 99cf1fb58e ("x86/virt/sev: Drop WBINVD before setting MSR_AMD64_SYSCFG_SNP_EN")
Reported-by: Srikanth Aithal <Srikanth.Aithal@amd.com>
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Srikanth Aithal <Srikanth.Aithal@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260707150033.2364758-1-tycho@kernel.org
Some multi GPU systems may have a VGA compatible device, but that might not be
used for display. If due to enumeration order this device is found before the
one actually used for display then multiple devices may show the boot_display
attribute, confusing userspace.
When screen info is valid, use it exclusively to find the primary device so
that only the device backing the framebuffer is reported. Only when no
framebuffer has been set up does it make sense to fall back to the default VGA
device. This ensures at most one primary graphics device, preferably the one
with the framebuffer.
Fixes: ad90860bd1 ("fbcon: Use screen info to find primary device")
Closes: https://lore.kernel.org/linux-pci/20260618081803.2790848-1-aaron.ma@canonical.com/#t
Reported-by: Aaron Ma <aaron.ma@canonical.com>
Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Aaron Ma <aaron.ma@canonical.com>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260623141505.1816786-1-mario.limonciello@amd.com
CPUs when Intel SNC (Sub-NUMA Clustering) is enabled
(Reinette Chatre)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fix from Ingo Molnar:
- Prevent OOB access in the resctrl code while offlining
CPUs when Intel SNC (Sub-NUMA Clustering) is enabled
(Reinette Chatre)
* tag 'x86-urgent-2026-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86,fs/resctrl: Prevent out-of-bounds access while offlining CPU when SNC enabled
- Fix a perf_event_attr::remove_on_exec bug for group
events (Taeyang Lee)
- Fix uprobes CALL emulation interaction with shadow stacks,
and add a testcase for this (David Windsor)
- Fix uprobes unregister bug (Jiri Olsa)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'perf-urgent-2026-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf events fixes from Ingo Molnar:
- Fix a perf_event_attr::remove_on_exec bug for group events
(Taeyang Lee)
- Fix uprobes CALL emulation interaction with shadow stacks, and
add a testcase for this (David Windsor)
- Fix uprobes unregister bug (Jiri Olsa)
* tag 'perf-urgent-2026-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
uprobes/x86: Use proper mm_struct in __in_uprobe_trampoline
selftests/x86: Add shadow stack uprobe CALL test
x86/uprobes: Keep shadow stack in sync for emulated CALLs
perf/core: Detach event groups during remove_on_exec
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Merge tag 'for-linus-7.2a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen fixes from Juergen Gross:
- rename function parameters and a comment related to
xen_exchange_memory() (Jan Beulich)
- replace __ASSEMBLY__ with __ASSEMBLER__ (Thomas Huth)
- add some sanity checking to the Xen pvcalls frontend driver (Michael
Bommarito)
- fix error handling in the Xen gntdev driver (Wentao Liang)
- fix several minor bugs in Xen related drivers (Yousef Alhouseen)
* tag 'for-linus-7.2a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
x86/Xen: correct commentary and parameter naming of xen_exchange_memory()
xenbus: reject unterminated directory replies
xen/gntalloc: validate grant count before allocation
xen/gntalloc: make grant counters unsigned
xen/front-pgdir-shbuf: free grant reference head on errors
xen/gntdev: fix error handling in ioctl
xen: Replace __ASSEMBLY__ with __ASSEMBLER__ in header files
xen/pvcalls: bound backend response req_id before indexing rsp[]
<linux/mod_devicetable.h> is included transitively in nearly every
driver in an x86_64 allmodconfig build of v7.1:
$ find drivers -name \*.o -not -name \*.mod.o | wc -l
21330
$ find drivers -name \*.o.cmd -not -name \*.mod.o.cmd | xargs grep -l mod_devicetable.h | wc -l
17038
The result of this mixture of different and unrelated subsystem details
is that even when touching an obscure device id struct most of the
kernel needs to be recompiled. Given that each driver typically only
needs one or two of these structures, splitting into per subsystem
headers and only including what is really needed reduces the amount of
needed recompilation.
This split is implemented in the first commit and then after some
preparatory work in the following commits, the last two replace
includes of <linux/mod_devicetable.h> by the actually needed more
specific headers. There are still a few instances left, but the ones
with high impact (that is in headers that are used a lot) and the easy
ones (.c files) are handled. These remaining includes will be addressed
during the next merge window.
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Merge tag 'device-id-rework' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux
Pull mod_devicetable.h header split from Uwe Kleine-König:
"Split <linux/mod_devicetable.h> in per subsystem headers
<linux/mod_devicetable.h> is included transitively in nearly every
driver in an x86_64 allmodconfig build of v7.1:
$ find drivers -name \*.o -not -name \*.mod.o | wc -l
21330
$ find drivers -name \*.o.cmd -not -name \*.mod.o.cmd | xargs grep -l mod_devicetable.h | wc -l
17038
The result of this mixture of different and unrelated subsystem
details is that even when touching an obscure device id struct most of
the kernel needs to be recompiled. Given that each driver typically
only needs one or two of these structures, splitting into per
subsystem headers and only including what is really needed reduces the
amount of needed recompilation.
This split is implemented in the first commit and then after some
preparatory work in the following commits, the last two replace
includes of <linux/mod_devicetable.h> by the actually needed more
specific headers.
There are still a few instances left, but the ones with high impact
(that is in headers that are used a lot) and the easy ones (.c files)
are handled. These remaining includes will be addressed during the
next merge window"
* tag 'device-id-rework' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux:
Replace <linux/mod_devicetable.h> by more specific <linux/device-id/*.h> (c files)
Replace <linux/mod_devicetable.h> by more specific <linux/device-id/*.h> (headers)
parisc: #include <linux/compiler.h> for unlikely() in <asm/ptrace.h>
media: em28xx: Add include for struct usb_device_id
LoongArch: KVM: Add include defining struct cpu_feature
ALSA: hda/core: Add include defining struct hda_device_id
usb: dwc2: Add include defining struct pci_device_id
platform/x86: int3472: Add include defining struct dmi_system_id
platform/x86: x86-android-tablets: Add include defining struct dmi_system_id
i2c: Let i2c-core.h include <linux/i2c.h>
of: Explicitly include <linux/types.h> and <linux/err.h>
platform/x86: msi-ec: Ensure dmi_system_id is defined
usb: serial: Include <linux/usb.h> in <linux/usb/serial.h>
driver core: platform: Include header for struct platform_device_id
driver: core: Include headers for acpi_device_id and of_device_id for struct device_driver
media: ti: vpe: #include <linux/platform_device.h> explicitly
mod_devicetable.h: Split into per subsystem headers
Replace the #include of <linux/mod_devicetable.h> by the more specific
<linux/device-id/*.h> where applicable. For most cases the include
can be dropped completely, only a few drivers need one or two headers
added.
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/1a3f2007c5c5dcf555c09a4035ce3ae8ef1b6c49.1782808461.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
