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authorMikulas Patocka <mpatocka@redhat.com>2015-02-17 14:34:00 -0500
committerMike Snitzer <snitzer@redhat.com>2015-02-18 09:41:54 -0500
commit22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3 (patch)
treeff93a13145102951cdc5302462175db52979ecdd /Documentation
parent2bec1f4a8832e74ebbe859f176d8a9cb20dd97f4 (diff)
dm snapshot: fix a possible invalid memory access on unload
When the snapshot target is unloaded, snapshot_dtr() waits until pending_exceptions_count drops to zero. Then, it destroys the snapshot. Therefore, the function that decrements pending_exceptions_count should not touch the snapshot structure after the decrement. pending_complete() calls free_pending_exception(), which decrements pending_exceptions_count, and then it performs up_write(&s->lock) and it calls retry_origin_bios() which dereferences s->origin. These two memory accesses to the fields of the snapshot may touch the dm_snapshot struture after it is freed. This patch moves the call to free_pending_exception() to the end of pending_complete(), so that the snapshot will not be destroyed while pending_complete() is in progress. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
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