diff mbox series

[4.14.y] dm: fix potential for q->make_request_fn NULL pointer

Message ID 20200213094928.30487-2-stefan.bader@canonical.com
State New
Headers show
Series [4.14.y] dm: fix potential for q->make_request_fn NULL pointer | expand

Commit Message

Stefan Bader Feb. 13, 2020, 9:49 a.m. UTC 
From: Mike Snitzer <snitzer@redhat.com>

[ Upstream commit 47ace7e012b9f7ad71d43ac9063d335ea3d6820b ]
Move blk_queue_make_request() to dm.c:alloc_dev() so that
q->make_request_fn is never NULL during the lifetime of a DM device
(even one that is created without a DM table).

Otherwise generic_make_request() will crash simply by doing:
  dmsetup create -n test
  mount /dev/dm-N /mnt

While at it, move ->congested_data initialization out of
dm.c:alloc_dev() and into the bio-based specific init method.

Reported-by: Stefan Bader <stefan.bader@canonical.com>
BugLink: https://bugs.launchpad.net/bugs/1860231
Fixes: ff36ab34583a ("dm: remove request-based logic from make_request_fn wrapper")
Depends-on: c12c9a3c3860c ("dm: various cleanups to md->queue initialization code")
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
[smb: adjusted for context and dm_init_md_queue() exitsting in older
      kernels]
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
---
 drivers/md/dm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index a56008b2e7c2..02ba6849f89d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1647,7 +1647,6 @@  void dm_init_md_queue(struct mapped_device *md)
 	 * - must do so here (in alloc_dev callchain) before queue is used
 	 */
 	md->queue->queuedata = md;
-	md->queue->backing_dev_info->congested_data = md;
 }
 
 void dm_init_normal_md_queue(struct mapped_device *md)
@@ -1658,6 +1657,7 @@  void dm_init_normal_md_queue(struct mapped_device *md)
 	/*
 	 * Initialize aspects of queue that aren't relevant for blk-mq
 	 */
+	md->queue->backing_dev_info->congested_data = md;
 	md->queue->backing_dev_info->congested_fn = dm_any_congested;
 }
 
@@ -1750,6 +1750,12 @@  static struct mapped_device *alloc_dev(int minor)
 		goto bad;
 
 	dm_init_md_queue(md);
+	/*
+	 * default to bio-based required ->make_request_fn until DM
+	 * table is loaded and md->type established. If request-based
+	 * table is loaded: blk-mq will override accordingly.
+	 */
+	blk_queue_make_request(md->queue, dm_make_request);
 
 	md->disk = alloc_disk_node(1, numa_node_id);
 	if (!md->disk)
@@ -2055,7 +2061,6 @@  int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
 	case DM_TYPE_BIO_BASED:
 	case DM_TYPE_DAX_BIO_BASED:
 		dm_init_normal_md_queue(md);
-		blk_queue_make_request(md->queue, dm_make_request);
 		/*
 		 * DM handles splitting bios as needed.  Free the bio_split bioset
 		 * since it won't be used (saves 1 process per bio-based DM device).