lkml.org 
[lkml]   [2024]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [bisected] Kernel v6.9-rc3 fails to boot on a Thinkpad T60 with MITIGATION_RETHUNK=y (regression from v6.8.5)
From
On 14.04.24 11:08, Borislav Petkov wrote:
> On Sun, Apr 14, 2024 at 10:36:26AM +0200, Borislav Petkov wrote:
>>> There was an earlier report about this here:
>>> https://lore.kernel.org/all/78e0d19c-b77a-4169-a80f-2eef91f4a1d6@gmail.com/
>> Am looking at the whole thing. Stay tuned...
>
> Something like this, I guess...
>
> Execution goes off somewhere into the weeds during alternatives patching
> of the return thunk while it tries to warn about it in the alternatives
> code itself and it all ends up in an endless INT3 exceptions due to our
> speculation blockers everywhere...
>
> I could chase it as to why exactly but the warning is there for all
> those mitigations which need a special return thunk and 32-bit doesn't
> need them (and at least the AMD untraining sequences are 64-bit only
> so...).

Erhard Furtner, did you try if this helps for a kernel with
MITIGATION_RETHUNK=y? Klara Modin, or could you give it a try?

Without a check this is unlikely to be merged and then more people might
run into problems like you two did.

Ciao, Thorsten
> IOW:
>
> diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
> index e674ccf720b9..391059b2c6fb 100644
> --- a/arch/x86/lib/retpoline.S
> +++ b/arch/x86/lib/retpoline.S
> @@ -382,8 +382,15 @@ SYM_FUNC_END(call_depth_return_thunk)
> SYM_CODE_START(__x86_return_thunk)
> UNWIND_HINT_FUNC
> ANNOTATE_NOENDBR
> +#if defined(CONFIG_MITIGATION_UNRET_ENTRY) || \
> + defined(CONFIG_MITIGATION_SRSO) || \
> + defined(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)
> ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE; ret), \
> "jmp warn_thunk_thunk", X86_FEATURE_ALWAYS
> +#else
> + ANNOTATE_UNRET_SAFE
> + ret
> +#endif
> int3
> SYM_CODE_END(__x86_return_thunk)
> EXPORT_SYMBOL(__x86_return_thunk)
>

\
 
 \ /
  Last update: 2024-04-17 10:39    [W:0.039 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site