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author | Junichi Nomura <j-nomura@ce.jp.nec.com> | 2015-11-17 09:36:56 (GMT) |
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committer | Mike Snitzer <snitzer@redhat.com> | 2015-11-17 19:19:00 (GMT) |
commit | 43e43c9ea60a7a1831ec823773e924d2dadefd44 (patch) | |
tree | ad17d6501aab2fc131ce103b8310941bf18c7b36 | |
parent | 647a20d5cad7477033bc021ec9dd75edf4bbf9a0 (diff) | |
download | linux-43e43c9ea60a7a1831ec823773e924d2dadefd44.tar.xz |
dm mpath: fix infinite recursion in ioctl when no paths and !queue_if_no_path
In multipath_prepare_ioctl(),
- pgpath is a path selected from available paths
- m->queue_io is true if we cannot send a request immediately to
paths, either because:
* there is no available path
* the path group needs activation (pg_init)
- pg_init is not started
- pg_init is still running
- m->queue_if_no_path is true if the device is configured to queue
I/O if there are no available paths
If !pgpath && !m->queue_if_no_path, the handler should return -EIO.
However in the course of refactoring the condition check has broken
and returns success in that case. Since bdev points to the dm device
itself, dm_blk_ioctl() calls __blk_dev_driver_ioctl() for itself and
recurses until crash.
You could reproduce the problem like this:
# dmsetup create mp --table '0 1024 multipath 0 0 0 0'
# sg_inq /dev/mapper/mp
<crash>
[ 172.648615] BUG: unable to handle kernel paging request at fffffffc81b10268
[ 172.662843] PGD 19dd067 PUD 0
[ 172.666269] Thread overran stack, or stack corrupted
[ 172.671808] Oops: 0000 [#1] SMP
...
Fix the condition check with some clarifications.
Fixes: e56f81e0b01e ("dm: refactor ioctl handling")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
-rw-r--r-- | drivers/md/dm-mpath.c | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 3d18292..cfa29f5 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -1537,29 +1537,31 @@ static int multipath_prepare_ioctl(struct dm_target *ti, struct block_device **bdev, fmode_t *mode) { struct multipath *m = ti->private; - struct pgpath *pgpath; unsigned long flags; int r; - r = 0; - spin_lock_irqsave(&m->lock, flags); if (!m->current_pgpath) __choose_pgpath(m, 0); - pgpath = m->current_pgpath; - - if (pgpath) { - *bdev = pgpath->path.dev->bdev; - *mode = pgpath->path.dev->mode; + if (m->current_pgpath) { + if (!m->queue_io) { + *bdev = m->current_pgpath->path.dev->bdev; + *mode = m->current_pgpath->path.dev->mode; + r = 0; + } else { + /* pg_init has not started or completed */ + r = -ENOTCONN; + } + } else { + /* No path is available */ + if (m->queue_if_no_path) + r = -ENOTCONN; + else + r = -EIO; } - if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path)) - r = -ENOTCONN; - else if (!*bdev) - r = -EIO; - spin_unlock_irqrestore(&m->lock, flags); if (r == -ENOTCONN) { |