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.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
d3c97900b4