From: "Borislav Petkov (AMD)" <bp@alien8.de> stable inclusion from stable-v5.10.253 commit ed7a3a246309ccc807238f1b4f159ee6d37ff9c4 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14370 CVE: CVE-2026-31628 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit e55d98e7756135f32150b9b8f75d580d0d4b2dd3 upstream. Zen1's hardware divider can leave, under certain circumstances, partial results from previous operations. Those results can be leaked by another, attacker thread. Fix that with a chicken bit. Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: arch/x86/kernel/cpu/amd.c [ context conflict] Signed-off-by: Zhang Kunbo <zhangkunbo@huawei.com> --- arch/x86/include/asm/msr-index.h | 3 +++ arch/x86/kernel/cpu/amd.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index a01922b0ed82..01175f84c89d 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -521,6 +521,9 @@ #define MSR_AMD64_DC_CFG 0xc0011022 #define MSR_AMD64_TW_CFG 0xc0011023 +#define MSR_AMD64_FP_CFG 0xc0011028 +#define MSR_AMD64_FP_CFG_ZEN1_DENORM_FIX_BIT 9 + #define MSR_AMD64_DE_CFG 0xc0011029 #define MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT 1 #define MSR_AMD64_DE_CFG_LFENCE_SERIALIZE BIT_ULL(MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index cb66f17855dd..b9944748634e 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1041,6 +1041,9 @@ static void init_amd_zen1(struct cpuinfo_x86 *c) msr_clear_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT); clear_cpu_cap(c, X86_FEATURE_IRPERF); } + + pr_notice_once("AMD Zen1 FPDSS bug detected, enabling mitigation.\n"); + msr_set_bit(MSR_AMD64_FP_CFG, MSR_AMD64_FP_CFG_ZEN1_DENORM_FIX_BIT); } static bool cpu_has_zenbleed_microcode(void) -- 2.34.1