6.6-stable review patch. If anyone has any objections, please let me know.
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From: Zheng Qixing zhengqixing@huawei.com
commit 8d33a030c566e1f105cd5bf27f37940b6367f3be upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/dm.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2688,7 +2688,7 @@ static int __dm_suspend(struct mapped_de { 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);
@@ -2740,7 +2740,7 @@ static int __dm_suspend(struct mapped_de * 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); } @@ -2752,7 +2752,8 @@ static int __dm_suspend(struct mapped_de * 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);