From: Michael Zhivich Date: Wed, 23 Jul 2025 13:40:19 +0000 (-0400) Subject: x86/bugs: Fix use of possibly uninit value in amd_check_tsa_microcode() X-Git-Tag: v6.1.148~207 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d37fe3982c0ee09c341b7b0d4b19e6fb608164aa;p=thirdparty%2Fkernel%2Fstable.git x86/bugs: Fix use of possibly uninit value in amd_check_tsa_microcode() For kernels compiled with CONFIG_INIT_STACK_NONE=y, the value of __reserved field in zen_patch_rev union on the stack may be garbage. If so, it will prevent correct microcode check when consulting p.ucode_rev, resulting in incorrect mitigation selection. This is a stable-only fix. Cc: Signed-off-by: Michael Zhivich Fixes: d12145e8454f ("x86/bugs: Add a Transient Scheduler Attacks mitigation") Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 4785d41558d61..2d71c329b3475 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -563,6 +563,8 @@ static bool amd_check_tsa_microcode(void) p.model = c->x86_model; p.ext_model = c->x86_model >> 4; p.stepping = c->x86_stepping; + /* reserved bits are expected to be 0 in test below */ + p.__reserved = 0; if (c->x86 == 0x19) { switch (p.ucode_rev >> 8) {