linux-kernel - Re: [PATCH] kernel.h: fix new warnings for container

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Date:   Tue, 20 Jun 2017 15:46:52 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Ian Abbott <abbotti@....co.uk>,
        Michal Nazarewicz <mina86@...a86.com>,
        Borislav Petkov <bp@...e.de>,
        Johannes Berg <johannes.berg@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Potapenko <glider@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel.h: fix new warnings for container_of()

On Tue, Jun 20, 2017 at 3:43 PM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Jun 20, 2017 at 1:09 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> I see new warnings with gcc-7.0.1 with the modified container_of():
>>
>> fs/f2fs/dir.c: In function 'F2FS_I':
>> fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types: 'struct f2fs_inode_info' and 'struct inode'
>
> This is actually from the randstruct plugin, not native gcc. I'll go
> update the message reporting to include a "randstruct: " which should
> make this more obvious.
>
>> This seems to happen for all structures that have a zero offset
>> between the member and the container structure, i.e. idential
>> pointers.
>>
>> Reverting to an intermediate pointer avoids the warning, and using
>> a void pointer instead of the target type should also avoid
>> regressing on the previous patch again.
>>
>> Fixes: mmotm ("kernel.h: handle pointers to arrays better in container_of()")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Thanks!
>
> I'll take this into the kspp tree so all the fixes are in the same place.

Oh, nevermind, I see the Fixes is for what's already in -mm. :) And I
see akpm picked this up already. Sorry for the noise!

-Kees

-- 
Kees Cook
Pixel Security