On Tue, Jul 22, 2025 at 08:28:44AM -0400, Michael Zhivich wrote:
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." so that the AI is happy. :-P
Cc: stable@vger.kernel.org Signed-off-by: Michael Zhivich mzhivich@akamai.com
Acked-by: Borislav Petkov (AMD) bp@alien8.de
Fixes: 7a0395f6607a5 ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
That commit in Fixes: is the 6.12 stable one.
The 6.6 one is:
Fixes: 90293047df18 ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
The 6.1 is:
Fixes: d12145e8454f ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
The 5.15 one:
Fixes: f2b75f1368af ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
and the 5.10 one is
Fixes: 78192f511f40 ("x86/bugs: Add a Transient Scheduler Attacks mitigation")
and since all stable kernels above have INIT_STACK_NONE, that same one-liner should be applied to all of them.
Greg, I'm thinking this one-liner should apply to all of the above with some fuzz. Can you simply add it to each stable version with a different Fixes: tag each?
Or do you prefer separate submissions?
Thx.
arch/x86/kernel/cpu/amd.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index efd42ee9d1cc..289ff197b1b3 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -378,6 +378,8 @@ 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 (cpu_has(c, X86_FEATURE_ZEN3) || cpu_has(c, X86_FEATURE_ZEN4)) { --