在 2025/10/22 16:45, Greg KH 写道:
On Wed, Oct 22, 2025 at 04:21:33PM +0800, Li Lingfeng wrote:
Hi,
在 2025/10/22 16:10, Greg KH 写道:
On Wed, Oct 22, 2025 at 04:01:04PM +0800, Li Lingfeng wrote:
Hi,
在 2025/10/14 11:03, Sasha Levin 写道:
From: Zheng Qixing zhengqixing@huawei.com
[ 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.
Fixes: c4576aed8d85 ("dm: fix request-based dm's use of dm_wait_for_completion") Cc: stable@vger.kernel.org Signed-off-by: Zheng Qixing zhengqixing@huawei.com Signed-off-by: Mikulas Patocka mpatocka@redhat.com [ omitted DMF_QUEUE_STOPPED flag setting and braces absent in 5.15 ] Signed-off-by: Sasha Levin sashal@kernel.org
drivers/md/dm.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 0868358a7a8d2..b51281ce15d4c 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2457,7 +2457,7 @@ 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);
@@ -2509,7 +2509,7 @@ 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);
It seems that before commit 80bd4a7aab4c ("blk-mq: move the srcu_struct used for quiescing to the tagset") was merged, blk_mq_wait_quiesce_done() would not attempt to access q->tag_set, so in dm_stop_queue() this kind of race condition would not cause a null pointer dereference. The change may not be necessary for 5.10, but adding it doesn’t appear to cause any issues either.
flush_workqueue(md->wq);@@ -2519,7 +2519,8 @@ 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);The fix tag c4576aed8d85 ("dm: fix request-based dm's use of dm_wait_for_completion") seems to correspond to the modification of dm_wait_for_completion().
if (!r) set_bit(dmf_suspended_flag, &md->flags);Perhaps adding another fix tag would be more appropriate?
Those tags come directly from the original commit.
Thanks for the clarification. Since the patch has already been merged into the mainline tree, we can't update the commit there. I was just wondering if it would be acceptable to add an additional “Fixes” tag when applying it to the stable branch, before merging.
I can, if needed, can you please provide that line?
Fixes: 80bd4a7aab4c ("blk-mq: move the srcu_struct used for quiescing to the tagset")
Thanks, Lingfeng
thanks,
greg k-h