[PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[Jim Mattson]

The linux-5.10-y backport of commit b377c66ae350 ("x86/retpoline: Add
NOENDBR annotation to the SRSO dummy return thunk") misplaced the new
NOENDBR annotation, repeating the annotation on __x86_return_thunk,
rather than adding the annotation to the !CONFIG_CPU_SRSO version of
srso_alias_untrain_ret, as intended.

Move the annotation to the right place.

Fixes: 0bdc64e9e716 ("x86/retpoline: Add NOENDBR annotation to the SRSO dummy return thunk")
Reported-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/lib/retpoline.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index ab9b047790dd..d1902213a0d6 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -105,6 +105,7 @@ __EXPORT_THUNK(srso_alias_untrain_ret)
 /* dummy definition for alternatives */
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	ANNOTATE_UNRET_SAFE
+	ANNOTATE_NOENDBR
 	ret
 	int3
 SYM_FUNC_END(srso_alias_untrain_ret)
@@ -258,7 +259,6 @@ SYM_CODE_START(__x86_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ANNOTATE_UNRET_SAFE
-	ANNOTATE_NOENDBR
 	ret
 	int3
 SYM_CODE_END(__x86_return_thunk)
-- 
2.45.2.803.g4e1b14247a-goog

Re: [PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[Borislav Petkov]

On Mon, Jul 08, 2024 at 09:43:05AM -0700, Jim Mattson wrote:
> The linux-5.10-y backport of commit b377c66ae350 ("x86/retpoline: Add
> NOENDBR annotation to the SRSO dummy return thunk") misplaced the new
> NOENDBR annotation, repeating the annotation on __x86_return_thunk,
> rather than adding the annotation to the !CONFIG_CPU_SRSO version of
> srso_alias_untrain_ret, as intended.
> 
> Move the annotation to the right place.
> 
> Fixes: 0bdc64e9e716 ("x86/retpoline: Add NOENDBR annotation to the SRSO dummy return thunk")
> Reported-by: Greg Thelen <gthelen@google.com>
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
>  arch/x86/lib/retpoline.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
> index ab9b047790dd..d1902213a0d6 100644
> --- a/arch/x86/lib/retpoline.S
> +++ b/arch/x86/lib/retpoline.S
> @@ -105,6 +105,7 @@ __EXPORT_THUNK(srso_alias_untrain_ret)
>  /* dummy definition for alternatives */
>  SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
>  	ANNOTATE_UNRET_SAFE
> +	ANNOTATE_NOENDBR
>  	ret
>  	int3
>  SYM_FUNC_END(srso_alias_untrain_ret)
> @@ -258,7 +259,6 @@ SYM_CODE_START(__x86_return_thunk)
>  	UNWIND_HINT_FUNC
>  	ANNOTATE_NOENDBR
>  	ANNOTATE_UNRET_SAFE
> -	ANNOTATE_NOENDBR

Whoops, those two here didn't look right, thanks for catching this.

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>

And looking at 6.1, it is wrong there too. :-\

commit 7ef6a7f9b32fdfc8bec0a10e6d5ac5374d4f02e7
Author: Borislav Petkov (AMD) <bp@alien8.de>
Date:   Fri Apr 5 16:46:37 2024 +0200

    x86/retpoline: Add NOENDBR annotation to the SRSO dummy return thunk
    
    commit b377c66ae3509ccea596512d6afb4777711c4870 upstream.

Greg (KH - there's another Greg on CC too :-)), do you prefer such stable-only
fixes like that or should we revert the wrong backports and redo them?

Thx!

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[Greg Kroah-Hartman]

On Mon, Jul 08, 2024 at 07:05:41PM +0200, Borislav Petkov wrote:
> On Mon, Jul 08, 2024 at 09:43:05AM -0700, Jim Mattson wrote:
> > The linux-5.10-y backport of commit b377c66ae350 ("x86/retpoline: Add
> > NOENDBR annotation to the SRSO dummy return thunk") misplaced the new
> > NOENDBR annotation, repeating the annotation on __x86_return_thunk,
> > rather than adding the annotation to the !CONFIG_CPU_SRSO version of
> > srso_alias_untrain_ret, as intended.
> > 
> > Move the annotation to the right place.
> > 
> > Fixes: 0bdc64e9e716 ("x86/retpoline: Add NOENDBR annotation to the SRSO dummy return thunk")
> > Reported-by: Greg Thelen <gthelen@google.com>
> > Signed-off-by: Jim Mattson <jmattson@google.com>
> > ---
> >  arch/x86/lib/retpoline.S | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
> > index ab9b047790dd..d1902213a0d6 100644
> > --- a/arch/x86/lib/retpoline.S
> > +++ b/arch/x86/lib/retpoline.S
> > @@ -105,6 +105,7 @@ __EXPORT_THUNK(srso_alias_untrain_ret)
> >  /* dummy definition for alternatives */
> >  SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
> >  	ANNOTATE_UNRET_SAFE
> > +	ANNOTATE_NOENDBR
> >  	ret
> >  	int3
> >  SYM_FUNC_END(srso_alias_untrain_ret)
> > @@ -258,7 +259,6 @@ SYM_CODE_START(__x86_return_thunk)
> >  	UNWIND_HINT_FUNC
> >  	ANNOTATE_NOENDBR
> >  	ANNOTATE_UNRET_SAFE
> > -	ANNOTATE_NOENDBR
> 
> Whoops, those two here didn't look right, thanks for catching this.
> 
> Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
> 
> And looking at 6.1, it is wrong there too. :-\
> 
> commit 7ef6a7f9b32fdfc8bec0a10e6d5ac5374d4f02e7
> Author: Borislav Petkov (AMD) <bp@alien8.de>
> Date:   Fri Apr 5 16:46:37 2024 +0200
> 
>     x86/retpoline: Add NOENDBR annotation to the SRSO dummy return thunk
>     
>     commit b377c66ae3509ccea596512d6afb4777711c4870 upstream.
> 
> Greg (KH - there's another Greg on CC too :-)), do you prefer such stable-only
> fixes like that or should we revert the wrong backports and redo them?

Sending fixups like this, for things that are already committed are
fine.  But note, someone needs to at least send them to the right place
(i.e. no one cc:ed stable@vger.kernel.org...) if they wish to see them
applied to a stable kernel...

thanks,

greg k-h

Re: [PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[Borislav Petkov]

On Tue, Jul 09, 2024 at 07:15:37AM +0200, Greg Kroah-Hartman wrote:
> Sending fixups like this, for things that are already committed are
> fine.  But note, someone needs to at least send them to the right place
> (i.e. no one cc:ed stable@vger.kernel.org...) if they wish to see them
> applied to a stable kernel...

Jim, should I or you want?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 5.10] x86/retpoline: Move a NOENDBR annotation to the SRSO dummy return thunk

[Jim Mattson]

On Tue, Jul 9, 2024 at 4:11 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Tue, Jul 09, 2024 at 07:15:37AM +0200, Greg Kroah-Hartman wrote:
> > Sending fixups like this, for things that are already committed are
> > fine.  But note, someone needs to at least send them to the right place
> > (i.e. no one cc:ed stable@vger.kernel.org...) if they wish to see them
> > applied to a stable kernel...
>
> Jim, should I or you want?

Done.

> Thx.
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette