Messages in this thread | | | Date | Wed, 17 Apr 2024 10:38:56 +0200 | Subject | Re: [bisected] Kernel v6.9-rc3 fails to boot on a Thinkpad T60 with MITIGATION_RETHUNK=y (regression from v6.8.5) | From | "Linux regression tracking (Thorsten Leemhuis)" <> |
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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) >
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