Ahmed S. Darwish 62af778005 x86/cpu: Sanitize CPUID(0x80000000) output ... [ Upstream commit cc663ba3fe ] CPUID(0x80000000).EAX returns the max extended CPUID leaf available. On x86-32 machines without an extended CPUID range, a CPUID(0x80000000) query will just repeat the output of the last valid standard CPUID leaf on the CPU; i.e., a garbage values. Current tip:x86/cpu code protects against this by doing: eax = cpuid_eax(0x80000000); c->extended_cpuid_level = eax; if ((eax & 0xffff0000) == 0x80000000) { // CPU has an extended CPUID range. Check for 0x80000001 if (eax >= 0x80000001) { cpuid(0x80000001, ...); } } This is correct so far. Afterwards though, the same possibly broken EAX value is used to check the availability of other extended CPUID leaves: if (c->extended_cpuid_level >= 0x80000007) ... if (c->extended_cpuid_level >= 0x80000008) ... if (c->extended_cpuid_level >= 0x8000000a) ... if (c->extended_cpuid_level >= 0x8000001f) ... which is invalid. Fix this by immediately setting the CPU's max extended CPUID leaf to zero if CPUID(0x80000000).EAX doesn't indicate a valid CPUID extended range. While at it, add a comment, similar to kernel/head_32.S, clarifying the CPUID(0x80000000) sanity check. References: 8a50e5135a ("x86-32: Use symbolic constants, safer CPUID when enabling EFER.NX") Fixes: 3da99c9776 ("x86: make (early)_identify_cpu more the same between 32bit and 64 bit") Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: John Ogness <john.ogness@linutronix.de> Cc: x86-cpuid@lists.linux.dev Link: https://lore.kernel.org/r/20250506050437.10264-3-darwi@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org>		2025-06-19 15:28:02 +02:00
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arm	ARM: at91: pm: fix at91_suspend_finish for ZQ calibration	2025-06-04 14:42:03 +02:00
arm64	arm64: dts: ti: k3-am68-sk: Fix regulator hierarchy	2025-06-04 14:42:24 +02:00
csky
hexagon
ia64
loongarch	LoongArch: Explicitly specify code model in Makefile	2025-05-22 14:12:25 +02:00
m68k
microblaze
mips	MIPS: pm-cps: Use per-CPU variables as per-CPU, not per-core	2025-06-04 14:42:06 +02:00
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openrisc
parisc	parisc: Fix double SIGFPE crash	2025-05-09 09:43:50 +02:00
powerpc	powerpc/crash: Fix non-smp kexec preparation	2025-06-19 15:28:02 +02:00
riscv	riscv: Allow NOMMU kernels to access all of RAM	2025-06-04 14:41:54 +02:00
s390	hypfs_create_cpu_files(): add missing check for hypfs_mkdir() failure	2025-06-04 14:41:57 +02:00
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sparc
um	um: let 'make clean' properly clean underlying SUBARCH as well	2025-06-04 14:42:25 +02:00
x86	x86/cpu: Sanitize CPUID(0x80000000) output	2025-06-19 15:28:02 +02:00
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