[PATCH] x86/bugs: Fix use of possibly uninit value in amd_check_tsa_microcode()

[Michael Zhivich]

Note: I believe this change only applies to stable backports.

For kernels compiled with CONFIG_INIT_STACK_NONE=y, the value of __reserved
bitfield 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.

Signed-off-by: Michael Zhivich <mzhivich@xxxxxxxxxx>
Fixes: 7a0395f6607a ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
---
 arch/x86/kernel/cpu/amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index efd42ee9d1cc..91b21814ce8c 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -371,7 +371,7 @@ static void bsp_determine_snp(struct cpuinfo_x86 *c)
 static bool amd_check_tsa_microcode(void)
 {
 	struct cpuinfo_x86 *c = &boot_cpu_data;
-	union zen_patch_rev p;
+	union zen_patch_rev p = {0};
 	u32 min_rev = 0;
 
 	p.ext_fam	= c->x86 - 0xf;
-- 
2.34.1