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x86/cacheinfo: Validate CPUID leaf 0x2 EDX output

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commit 8177c6bedb7013cf736137da586cf783922309dd upstream.

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.

The historical Git commit:

  019361a20f016 ("- pre6: Intel: start to add Pentium IV specific stuff (128-byte cacheline etc)...")

introduced leaf 0x2 output parsing.  It only validated the MSBs of EAX,
EBX, and ECX, but left EDX unchecked.

Validate EDX's most-significant bit.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250304085152.51092-2-darwi@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ahmed S. Darwish
2025-03-04 09:51:12 +01:00
committed by Greg Kroah-Hartman
parent 85e3d5ba5d
commit cfe0ecf6ce
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/cpu/cacheinfo.c
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@@ -801,7 +801,7 @@ void init_intel_cacheinfo(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;