FAILED: patch "[PATCH] dm: fix NULL pointer dereference in __dm_suspend()" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 8d33a030c566e1f105cd5bf27f37940b6367f3be
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025101316-handmade-imaginary-edf0@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8d33a030c566e1f105cd5bf27f37940b6367f3be Mon Sep 17 00:00:00 2001
From: Zheng Qixing <[email protected]>
Date: Tue, 26 Aug 2025 15:42:04 +0800
Subject: [PATCH] dm: fix NULL pointer dereference in __dm_suspend()

There is a race condition between dm device suspend and table load that can lead to null pointer dereference. The issue occurs when suspend is invoked before table load completes:

BUG: kernel NULL pointer dereference, address: 0000000000000054
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 6 PID: 6798 Comm: dmsetup Not tainted 6.6.0-g7e52f5f0ca9b #62
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
RIP: 0010:blk_mq_wait_quiesce_done+0x0/0x50
Call Trace:
  <TASK>
  blk_mq_quiesce_queue+0x2c/0x50
  dm_stop_queue+0xd/0x20
  __dm_suspend+0x130/0x330
  dm_suspend+0x11a/0x180
  dev_suspend+0x27e/0x560
  ctl_ioctl+0x4cf/0x850
  dm_ctl_ioctl+0xd/0x20
  vfs_ioctl+0x1d/0x50
  __se_sys_ioctl+0x9b/0xc0
  __x64_sys_ioctl+0x19/0x30
  x64_sys_call+0x2c4a/0x4620
  do_syscall_64+0x9e/0x1b0

The issue can be triggered as below:

T1 T2
dm_suspend table_load
__dm_suspend dm_setup_md_queue

						dm_mq_init_request_queue
						blk_mq_init_allocated_queue
						=> q->mq_ops = set->ops; (1)
dm_stop_queue / dm_wait_for_completion
=> q->tag_set NULL pointer!	(2)
						=> q->tag_set = set; (3)

Fix this by checking if a valid table (map) exists before performing request-based suspend and waiting for target I/O. When map is NULL, skip these table-dependent suspend steps.

Even when map is NULL, no I/O can reach any target because there is no table loaded; I/O submitted in this state will fail early in the DM layer. Skipping the table-dependent suspend logic in this case is safe and avoids NULL pointer dereferences.

index 7222f20c1a83..66dd5f6ce778 100644
@@ -2908,7 +2908,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 {
 	bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG;
 	bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG;
-	int r;
+	int r = 0;
 
 	lockdep_assert_held(&md->suspend_lock);
 

@@ -2960,7 +2960,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 	 * Stop md->queue before flushing md->wq in case request-based
 	 * dm defers requests to md->wq from md->queue.
 	 */
-	if (dm_request_based(md)) {
+	if (map && dm_request_based(md)) {
 		dm_stop_queue(md->queue);
 		set_bit(DMF_QUEUE_STOPPED, &md->flags);
 	}

@@ -2972,7 +2972,8 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 	 * We call dm_wait_for_completion to wait for all existing requests
 	 * to finish.
 	 */
-	r = dm_wait_for_completion(md, task_state);
+	if (map)
+		r = dm_wait_for_completion(md, task_state);
 	if (!r)
 		set_bit(dmf_suspended_flag, &md->flags);
 

From: Zheng Qixing <[email protected]>

[ Upstream commit 8d33a030c566e1f105cd5bf27f37940b6367f3be ]

There is a race condition between dm device suspend and table load that can lead to null pointer dereference. The issue occurs when suspend is invoked before table load completes:

BUG: kernel NULL pointer dereference, address: 0000000000000054
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 6 PID: 6798 Comm: dmsetup Not tainted 6.6.0-g7e52f5f0ca9b #62
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
RIP: 0010:blk_mq_wait_quiesce_done+0x0/0x50
Call Trace:
  <TASK>
  blk_mq_quiesce_queue+0x2c/0x50
  dm_stop_queue+0xd/0x20
  __dm_suspend+0x130/0x330
  dm_suspend+0x11a/0x180
  dev_suspend+0x27e/0x560
  ctl_ioctl+0x4cf/0x850
  dm_ctl_ioctl+0xd/0x20
  vfs_ioctl+0x1d/0x50
  __se_sys_ioctl+0x9b/0xc0
  __x64_sys_ioctl+0x19/0x30
  x64_sys_call+0x2c4a/0x4620
  do_syscall_64+0x9e/0x1b0

The issue can be triggered as below:

T1 T2
dm_suspend table_load
__dm_suspend dm_setup_md_queue

						dm_mq_init_request_queue
						blk_mq_init_allocated_queue
						=> q->mq_ops = set->ops; (1)
dm_stop_queue / dm_wait_for_completion
=> q->tag_set NULL pointer!	(2)
						=> q->tag_set = set; (3)

Fix this by checking if a valid table (map) exists before performing request-based suspend and waiting for target I/O. When map is NULL, skip these table-dependent suspend steps.

Even when map is NULL, no I/O can reach any target because there is no table loaded; I/O submitted in this state will fail early in the DM layer. Skipping the table-dependent suspend logic in this case is safe and avoids NULL pointer dereferences.

---
 drivers/md/dm.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

index 3d00bb98d702b..be7182adcdd5b 100644
@@ -2595,7 +2595,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 {
 	bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG;
 	bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG;
-	int r;
+	int r = 0;
 
 	lockdep_assert_held(&md->suspend_lock);
 

@@ -2648,7 +2648,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 	 * Stop md->queue before flushing md->wq in case request-based
 	 * dm defers requests to md->wq from md->queue.
 	 */
-	if (dm_request_based(md))
+	if (map && dm_request_based(md))
 		dm_stop_queue(md->queue);
 
 	flush_workqueue(md->wq);

@@ -2658,7 +2658,8 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
 	 * We call dm_wait_for_completion to wait for all existing requests
 	 * to finish.
 	 */
-	r = dm_wait_for_completion(md, task_state);
+	if (map)
+		r = dm_wait_for_completion(md, task_state);
 	if (!r)
 		set_bit(dmf_suspended_flag, &md->flags);
 

2.51.0