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linux/arch/x86
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Brian Geffon bae7fc6f0d x86/fpu: Correct pkru/xstate inconsistency 
When eagerly switching PKRU in switch_fpu_finish() it checks that
current is not a kernel thread as kernel threads will never use PKRU.
It's possible that this_cpu_read_stable() on current_task
(ie. get_current()) is returning an old cached value. To resolve this
reference next_p directly rather than relying on current.

As written it's possible when switching from a kernel thread to a
userspace thread to observe a cached PF_KTHREAD flag and never restore
the PKRU. And as a result this issue only occurs when switching
from a kernel thread to a userspace thread, switching from a non kernel
thread works perfectly fine because all that is considered in that
situation are the flags from some other non kernel task and the next fpu
is passed in to switch_fpu_finish().

This behavior only exists between 5.2 and 5.13 when it was fixed by a
rewrite decoupling PKRU from xstate, in:
  commit 954436989c ("x86/fpu: Remove PKRU handling from switch_fpu_finish()")

Unfortunately backporting the fix from 5.13 is probably not realistic as
it's part of a 60+ patch series which rewrites most of the PKRU handling.

Fixes: 0cecca9d03 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Brian Geffon <bgeffon@google.com>
Signed-off-by: Willis Kung <williskung@google.com>
Tested-by: Willis Kung <williskung@google.com>
Cc: <stable@vger.kernel.org> # v5.4.x
Cc: <stable@vger.kernel.org> # v5.10.x
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-03-02 11:42:47 +01:00
..
boot x86/boot/compressed: Move CLANG_FLAGS to beginning of KBUILD_CFLAGS 2022-01-27 10:54:00 +01:00
configs x86/kbuild: Enable CONFIG_KALLSYMS_ALL=y in the defconfigs 2022-01-27 10:54:21 +01:00
crypto crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit 2021-07-14 16:56:06 +02:00
entry x86/entry: Add a fence for kernel entry SWAPGS in paranoid_entry() 2021-12-08 09:03:27 +01:00
events x86/perf: Avoid warning for Arch LBR without XSAVE 2022-02-16 12:54:18 +01:00
hyperv x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails 2021-11-26 10:39:19 +01:00
ia32
include x86/fpu: Correct pkru/xstate inconsistency 2022-03-02 11:42:47 +01:00
kernel x86/fpu: Correct pkru/xstate inconsistency 2022-03-02 11:42:47 +01:00
kvm KVM: x86/mmu: make apf token non-zero to fix bug 2022-03-02 11:42:46 +01:00
lib x86/iopl: Fake iopl(3) CLI/STI usage 2021-11-21 13:46:36 +01:00
math-emu
mm x86/sev: Make the #VC exception stacks part of the default stacks storage 2021-11-18 14:04:32 +01:00
net bpf: Handle return value of BPF_PROG_TYPE_STRUCT_OPS prog 2021-10-06 15:55:50 +02:00
oprofile
pci PCI: Add AMD RS690 quirk to enable 64-bit DMA 2021-06-30 08:47:23 -04:00
platform x86/sme: Explicitly map new EFI memmap table as encrypted 2021-12-14 11:32:35 +01:00
power PM: hibernate: x86: Use crc32 instead of md5 for hibernation e820 integrity check 2021-05-14 09:50:21 +02:00
purgatory
ras
realmode x86/mm: Flush global TLB when switching to trampoline page-table 2022-01-27 10:54:14 +01:00
tools x86/tools: Fix objdump version check again 2021-08-18 08:59:15 +02:00
um um: registers: Rename function names to avoid conflicts and build problems 2022-01-27 10:54:18 +01:00
video
xen x86/Xen: streamline (and fix) PV CPU enumeration 2022-02-23 12:01:00 +01:00
.gitignore
Kbuild
Kconfig x86/sme: Explicitly map new EFI memmap table as encrypted 2021-12-14 11:32:35 +01:00
Kconfig.assembler
Kconfig.cpu
Kconfig.debug
Makefile x86/build: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS) 2021-05-11 14:47:18 +02:00
Makefile_32.cpu
Makefile.um