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authorMikulas Patocka <mpatocka@redhat.com>2015-02-17 20:34:00 +0100
committerMike Snitzer <snitzer@redhat.com>2015-02-18 15:41:54 +0100
commit22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3 (patch)
treeff93a13145102951cdc5302462175db52979ecdd /drivers
parentdm: fix a race condition in dm_get_md (diff)
downloadlinux-22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3.tar.xz
linux-22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3.zip
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
Diffstat (limited to 'drivers')
-rw-r--r--drivers/md/dm-snap.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 864b03f47727..8b204ae216ab 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1432,8 +1432,6 @@ out:
full_bio->bi_private = pe->full_bio_private;
atomic_inc(&full_bio->bi_remaining);
}
- free_pending_exception(pe);
-
increment_pending_exceptions_done_count();
up_write(&s->lock);
@@ -1450,6 +1448,8 @@ out:
}
retry_origin_bios(s, origin_bios);
+
+ free_pending_exception(pe);
}
static void commit_callback(void *context, int success)