mirror: Fail gracefully for source == target
commit86fae10c64d642256cf019e6829929fa0d259c7a
authorKevin Wolf <kwolf@redhat.com>
Tue, 14 Aug 2018 09:52:25 +0000 (14 11:52 +0200)
committerKevin Wolf <kwolf@redhat.com>
Wed, 15 Aug 2018 10:50:39 +0000 (15 12:50 +0200)
tree00b6eb0df7a2de3d00cb1ccc2b3a5d92da5688b6
parentdbfdf6cb3625c68d0ea84ace4a786406cf43d4f3
mirror: Fail gracefully for source == target

blockdev-mirror with the same node for source and target segfaults
today: A node is in its own backing chain, so mirror_start_job() decides
that this is an active commit. When adding the intermediate nodes with
block_job_add_bdrv(), it starts the iteration through the subchain with
the backing file of source, though, so it never reaches target and
instead runs into NULL at the base.

While we could fix that by starting with source itself, there is no
point in allowing mirroring a node into itself and I wouldn't be
surprised if this caused more problems later.

So just check for this scenario and error out.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
block/mirror.c
tests/qemu-iotests/041
tests/qemu-iotests/041.out