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SubjectRe: [PATCH] mm: fix overly aggressive shmdt() when calls span multiple segments
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On Mon, 2014-11-03 at 16:06 -0800, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> This is a highly-contrived scenario. But, a single shmdt() call
> can be induced in to unmapping memory from mulitple shm segments.
> Example code is here:
>
> http://www.sr71.net/~dave/intel/shmfun.c
>
> The fix is pretty simple: Record the 'struct file' for the first
> VMA we encounter and then stick to it. Decline to unmap anything
> not from the same file and thus the same segment.
>
> I found this by inspection and the odds of anyone hitting this in
> practice are pretty darn small.
>
> Lightly tested, but it's a pretty small patch.

Passed shmdt ltp tests, fwiw.

> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>



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