x86/cpu: Validate CPUID leaf 0x2 EDX output

commit 1881148215c67151b146450fb89ec22fd92337a7 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.

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: e0ba94f14f74 ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index a7a8c7731c1a4c937cb7b5ef96cf42b5fc8d1efd..6bff5096488d739be84bd22a53b71033ac1687af 100644 (file)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -911,7 +911,7 @@ 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;