From e41f30294b426c6337aa182dc5adc4fea8d2a68a Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Tue, 17 Feb 2015 14:34:00 -0500 Subject: [PATCH] dm snapshot: fix a possible invalid memory access on unload commit 22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3 upstream. 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 Signed-off-by: Mike Snitzer Signed-off-by: Ben Hutchings --- Reading git-format-patch failed