This is a note to let you know that I've just added the patch titled
x86/retpoline: Do the necessary fixup to the Zen3/4 srso return thunk for !SRSO
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-retpoline-do-the-necessary-fixup-to-the-zen3-4-srso-return-thunk-for-srso.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0e110732473e14d6520e49d75d2c88ef7d46fe67 Mon Sep 17 00:00:00 2001
From: "Borislav Petkov (AMD)" <bp@xxxxxxxxx>
Date: Tue, 2 Apr 2024 16:05:49 +0200
Subject: x86/retpoline: Do the necessary fixup to the Zen3/4 srso return thunk for !SRSO
From: Borislav Petkov (AMD) <bp@xxxxxxxxx>
commit 0e110732473e14d6520e49d75d2c88ef7d46fe67 upstream.
The srso_alias_untrain_ret() dummy thunk in the !CONFIG_MITIGATION_SRSO
case is there only for the altenative in CALL_UNTRAIN_RET to have
a symbol to resolve.
However, testing with kernels which don't have CONFIG_MITIGATION_SRSO
enabled, leads to the warning in patch_return() to fire:
missing return thunk: srso_alias_untrain_ret+0x0/0x10-0x0: eb 0e 66 66 2e
WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:826 apply_returns (arch/x86/kernel/alternative.c:826
Put in a plain "ret" there so that gcc doesn't put a return thunk in
in its place which special and gets checked.
In addition:
ERROR: modpost: "srso_alias_untrain_ret" [arch/x86/kvm/kvm-amd.ko] undefined!
make[2]: *** [scripts/Makefile.modpost:145: Module.symvers] Chyba 1
make[1]: *** [/usr/src/linux-6.8.3/Makefile:1873: modpost] Chyba 2
make: *** [Makefile:240: __sub-make] Chyba 2
since !SRSO builds would use the dummy return thunk as reported by
petr.pisar@xxxxxxxx, https://bugzilla.kernel.org/show_bug.cgi?id=218679.
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202404020901.da75a60f-oliver.sang@xxxxxxxxx
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/all/202404020901.da75a60f-oliver.sang@xxxxxxxxx/
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/lib/retpoline.S | 1 +
1 file changed, 1 insertion(+)
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -110,6 +110,7 @@ SYM_START(srso_alias_untrain_ret, SYM_L_
ret
int3
SYM_FUNC_END(srso_alias_untrain_ret)
+__EXPORT_THUNK(srso_alias_untrain_ret)
#endif
SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
Patches currently in stable-queue which might be from bp@xxxxxxxxx are
queue-6.1/x86-bugs-fix-the-srso-mitigation-on-zen3-4.patch
queue-6.1/x86-retpoline-do-the-necessary-fixup-to-the-zen3-4-srso-return-thunk-for-srso.patch
