Re: [PATCH] x86/extable: ensure entries are swapped completely when sorting

[Mathias Krause]

On 11 May 2016 at 07:46, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> On 10 May 2016 at 23:07, Mathias Krause <minipli@xxxxxxxxxxxxxx> wrote:
>> The x86 exception table sorting was changed in commit 29934b0fb8ff
>> ("x86/extable: use generic search and sort routines") to use the arch
>> independent code in lib/extable.c. However, the patch was mangled
>> somehow on its way into the kernel from the last version posted at [1].
>> The committed version kind of attempted to incorporate the changes of
>> commit 548acf19234d ("x86/mm: Expand the exception table logic to allow
>> new handling options") as in _completely_ _ignoring_ the x86 specific
>> 'handler' member of struct exception_table_entry. This effectively broke
>> the sorting as entries will only partly be swapped now.
>>
>
> OK, it appears that Tony's patches grew a 'handler' field fairly late
> in their review cycle, and I didn't pick up on that. Apologies.

No need to apologize, as your patch *must* have created conflicts for
the committer applying it. It's just that those conflicts were
resolved wrongly. He/She should have asked you for a new version,
but... did not :/

>> Fortunately, the x86 Kconfig selects BUILDTIME_EXTABLE_SORT, so the
>> exception table doesn't need to be sorted at runtime. However, in case
>> that ever changes, we better not break the exception table sorting just
>> because of that.
>>
>
> BUILDTIME_EXTABLE_SORT applies to the core image only, but we still
> rely on the sorting routines for modules in that case. So I think this
> needs to be fixed right away.

Good point!

>
>> Fix this by providing a swap_ex_entry_fixup() macro that takes care of
>> the 'handler' member.
>>
>> [1] https://lkml.org/lkml/2016/1/27/232
>>
>> Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
>> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> Cc: Borislav Petkov <bp@xxxxxxx>
>> Cc: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
>> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> Cc: Tony Luck <tony.luck@xxxxxxxxx>
>
> Fixes: 29934b0fb8f ("x86/extable: use generic search and sort routines")
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>
> Thanks,
> Ard.
>

Thanks,
Mathias