Re: [PATCH] 2.4: Fix steal_locks race

[Andreas Gruenbacher]

On Sat, 9 Aug 2003, Herbert Xu wrote:

> On Fri, Aug 08, 2003 at 08:53:21PM +1000, herbert wrote:
> >
> > The steal_locks() call in binfmt_elf.c is buggy.  It steals locks from
> > a files entry whose reference was dropped much earlier.  This allows it
> > to steal other process's locks.
> >
> > The following patch calls steal_locks() earlier so that this does not
> > happen.
>
> My patch is buggy too.  If a file is closed by another clone between
> the two steal_locks calls the lock will again be lost.  Fortunately
> this much harder to trigger than the previous bug.

I think this is not a strict bug---this scenario is not covered by POSIX
in the first place. Unless lock stealing is done atomically with
unshare_files there is a window of oportunity between unshare_files() and
steal_locks(), so locks can still get lost.


Cheers,
Andreas.
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