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x86/cpu: Validate CPUID leaf 0x2 EDX output

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CPUID leaf 0x2 emits one-byte descriptors in its four output registers
EAX, EBX, ECX, and EDX.  For these descriptors to be valid, the most
significant bit (MSB) of each register must be clear.

Leaf 0x2 parsing at intel.c only validated the MSBs of EAX, EBX, and
ECX, but left EDX unchecked.

Validate EDX's most-significant bit as well.

Fixes: e0ba94f14f ("x86/tlb_info: get last level TLB entry number of CPU")
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250304085152.51092-3-darwi@linutronix.de
This commit is contained in:
Ahmed S. Darwish 2025-03-04 09:51:13 +01:00 committed by Ingo Molnar
parent 8177c6bedb
commit 1881148215
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/cpu/intel.c
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@ -799,7 +799,7 @@ static void intel_detect_tlb(struct cpuinfo_x86 *c)
cpuid(2, &regs[0], &regs[1], &regs[2], &regs[3]);
/* If bit 31 is set, this is an unknown format */
for (j = 0 ; j < 3 ; j++)
for (j = 0 ; j < 4 ; j++)
if (regs[j] & (1 << 31))
regs[j] = 0;