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 <[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. > > > > > > > > Fixes: c4576aed8d85 ("dm: fix request-based dm's use of > > > > dm_wait_for_completion") > > > > Cc: [email protected] > > > > Signed-off-by: Zheng Qixing <[email protected]> > > > > Signed-off-by: Mikulas Patocka <[email protected]> > > > > [ omitted DMF_QUEUE_STOPPED flag setting and braces absent in 5.15 ] > > > > Signed-off-by: Sasha Levin <[email protected]> > > > > --- > > > > 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? thanks, greg k-h
