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07212d16ad
syzkaller has found another ugly race in the VGIC, this time dealing
with VGIC creation. Since kvm_vgic_create() doesn't sufficiently protect
against in-flight vCPU creations, it is possible to get a vCPU into the
kernel w/ an in-kernel VGIC but no allocation of private IRQs:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000d20
Mem abort info:
ESR = 0x0000000096000046
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000
CM = 0, WnR = 1, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000103e4f000
[0000000000000d20] pgd=0800000102e1c403, p4d=0800000102e1c403, pud=0800000101146403, pmd=0000000000000000
Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP
CPU: 9 UID: 0 PID: 246 Comm: test Not tainted 6.14.0-rc6-00097-g0c90821f5db8 #16
Hardware name: linux,dummy-virt (DT)
pstate: 814020c5 (Nzcv daIF +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : _raw_spin_lock_irqsave+0x34/0x8c
lr : kvm_vgic_set_owner+0x54/0xa4
sp : ffff80008086ba20
x29: ffff80008086ba20 x28: ffff0000c19b5640 x27: 0000000000000000
x26: 0000000000000000 x25: ffff0000c4879bd0 x24: 000000000000001e
x23: 0000000000000000 x22: 0000000000000000 x21: ffff0000c487af80
x20: ffff0000c487af18 x19: 0000000000000000 x18: 0000001afadd5a8b
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000001
x14: ffff0000c19b56c0 x13: 0030c9adf9d9889e x12: ffffc263710e1908
x11: 0000001afb0d74f2 x10: e0966b840b373664 x9 : ec806bf7d6a57cd5
x8 : ffff80008086b980 x7 : 0000000000000001 x6 : 0000000000000001
x5 : 0000000080800054 x4 : 4ec4ec4ec4ec4ec5 x3 : 0000000000000000
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000d20
Call trace:
_raw_spin_lock_irqsave+0x34/0x8c (P)
kvm_vgic_set_owner+0x54/0xa4
kvm_timer_enable+0xf4/0x274
kvm_arch_vcpu_run_pid_change+0xe0/0x380
kvm_vcpu_ioctl+0x93c/0x9e0
__arm64_sys_ioctl+0xb4/0xec
invoke_syscall+0x48/0x110
el0_svc_common.constprop.0+0x40/0xe0
do_el0_svc+0x1c/0x28
el0_svc+0x30/0xd0
el0t_64_sync_handler+0x10c/0x138
el0t_64_sync+0x198/0x19c
Code: b9000841 d503201f 52800001 52800022 (88e17c02)
---[ end trace 0000000000000000 ]---
Plug the race by explicitly checking for an in-progress vCPU creation
and failing kvm_vgic_create() when that's the case. Add some comments to
document all the things kvm_vgic_create() is trying to guard against
too.
Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Tested-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20250523194722.4066715-6-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>
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| arch | ||
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
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| samples | ||
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| security | ||
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| tools | ||
| usr | ||
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| .clang-format | ||
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| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
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| COPYING | ||
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| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.