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Commit ad6026d2 authored by Mike Snitzer's avatar Mike Snitzer Committed by Greg Kroah-Hartman
Browse files

dm: fix potential for q->make_request_fn NULL pointer 



commit 47ace7e012b9f7ad71d43ac9063d335ea3d6820b upstream.

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: default avatarStefan Bader <stefan.bader@canonical.com>
BugLink: https://bugs.launchpad.net/bugs/1860231


Fixes: ff36ab34 ("dm: remove request-based logic from make_request_fn wrapper")
Depends-on: c12c9a3c ("dm: various cleanups to md->queue initialization code")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
[smb: adjusted for context and dm_init_md_queue() exitsting in older
      kernels]
Signed-off-by: default avatarStefan Bader <stefan.bader@canonical.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f2cfc606

drivers/md/dm.c

+7 −2
Original line number Diff line number Diff line
@@ -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).