Re: [PATCH v2] fs: select: fix information leak to userspace

[AmÃrico Wang]

On Wed, Nov 24, 2010 at 10:44:50AM +0000, PÃdraig Brady wrote:
>On 23/11/10 18:02, Andreas Dilger wrote:
>> On 2010-11-23, at 07:45, walter harms wrote:
>>> Maybe we can convince the gcc people to make 0 padding default. That will not solve the problems for other compilers but when they claim "works like gcc" we can press then to support this also. I can imagine that this will close some other subtle leaks also.
>> 
>> It makes the most sense to tackle this at the GCC level, since the added overhead of doing memset(0) on the whole struct may be non-trivial for commonly-used and/or large structures.  Since GCC is already explicitly zeroing the _used_ fields in the struct, it can much more easily determine whether there is padding in the structure, and zero those few bytes as needed.
>
>Zero padding structs is part of C90. Details here:
>http://www.pixelbeat.org/programming/gcc/auto_init.html

Nope.

>
>gcc doesn't zero pad when _all_ elements are specified.
>

That is what gcc does, not what C standard specifies.
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