[PATCH] dm: do not assign error to md->kworker_task
From: Tahsin Erdogan
Date: Mon Oct 17 2016 - 21:17:16 EST
cleanup_mapped_device() calls kthread_stop() if kworker_task is
non-NULL. Currently the assigned value could be a valid task struct or
an error code. Do not assign in case of error.
Example failure when kthread_run() returns -ENOMEM:
[ 22.255939] BUG: unable to handle kernel NULL pointer dereference at 000000000000000c
[ 22.258847] IP: [<ffffffff802973a4>] kthread_stop+0x34/0x260
[ 22.260130] PGD 78a23067 PUD 78b56067 PMD 0
[ 22.260130] Oops: 0002 [#1] SMP
[ 22.260130] CPU: 1 PID: 1849 Comm: dmsetup Tainted: G W 4.8.0+ #3
[ 22.260130] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[ 22.260130] task: ffff880078966400 task.stack: ffffc90001898000
[ 22.260130] RIP: 0010:[<ffffffff802973a4>] [<ffffffff802973a4>] kthread_stop+0x34/0x260
[ 22.260130] RSP: 0018:ffffc9000189bc40 EFLAGS: 00010202
[ 22.260130] RAX: 0000000000000001 RBX: fffffffffffffff4 RCX: 0000000000000003
[ 22.260130] RDX: ffff88007fd18600 RSI: 0000000000000001 RDI: ffffffff81037080
[ 22.260130] RBP: ffffc9000189bc50 R08: 0000000000000000 R09: 0000000000000000
[ 22.260130] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
[ 22.260130] R13: 0000000000000001 R14: ffff880077f539d8 R15: 0000000000000004
[ 22.260130] FS: 00007fc9ef2e2840(0000) GS:ffff88007fd00000(0000) knlGS:0000000000000000
[ 22.260130] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 22.260130] CR2: 000000000000000c CR3: 0000000077fa2000 CR4: 00000000000006e0
[ 22.260130] Stack:
[ 22.260130] ffff880077f53800 0000000000000000 ffffc9000189bc68 ffffffff808b26fa
[ 22.260130] ffff880077f53800 ffffc9000189bcb0 ffffffff808b3c58 0000000000000000
[ 22.260130] 00000000808b534b ffffc9000189bd20 ffff880077f53800 0000000000000000
[ 22.260130] Call Trace:
[ 22.260130] [<ffffffff808b26fa>] cleanup_mapped_device+0x2a/0xe0
[ 22.260130] [<ffffffff808b3c58>] __dm_destroy+0x1a8/0x2b0
[ 22.260130] [<ffffffff808b4b6e>] dm_destroy+0xe/0x10
[ 22.260130] [<ffffffff808b9f49>] dev_remove+0xd9/0x120
[ 22.260130] [<ffffffff808b9e70>] ? dev_suspend+0x210/0x210
[ 22.260130] [<ffffffff808ba576>] ctl_ioctl+0x206/0x500
[ 22.260130] [<ffffffff808ba87e>] dm_ctl_ioctl+0xe/0x20
[ 22.260130] [<ffffffff803bca40>] do_vfs_ioctl+0x90/0x6b0
[ 22.260130] [<ffffffff80b11fd7>] ? entry_SYSCALL_64_fastpath+0x5/0xad
[ 22.260130] [<ffffffff802bd974>] ? trace_hardirqs_on_caller+0xf4/0x1c0
[ 22.260130] [<ffffffff803bd0d4>] SyS_ioctl+0x74/0x80
[ 22.260130] [<ffffffff80b11fea>] entry_SYSCALL_64_fastpath+0x18/0xad
[ 22.260130] Code: e5 41 54 85 c0 53 48 89 fb 0f 8f bb 01 00 00 65 8b
05 a1 2d d7 7f 89 c0 48 0f a3 05 9f 94 e8 00 0f 92 c0 84 c0 0f 85 a3 00
00 00 <f0> ff 43 18 48 89 df e8 10 f8 ff ff 48 85 c0 49 89 c4 74 29 f0
[ 22.260130] RIP [<ffffffff802973a4>] kthread_stop+0x34/0x260
[ 22.260130] RSP <ffffc9000189bc40>
[ 22.260130] CR2: 000000000000000c
[ 22.301062] ---[ end trace 22b4f4f62c04f3cf ]---
Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
---
drivers/md/dm-rq.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 5eacce1ef88b..6e5197414a57 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -841,6 +841,8 @@ static void dm_old_request_fn(struct request_queue *q)
*/
int dm_old_init_request_queue(struct mapped_device *md)
{
+ struct task_struct *task;
+
/* Fully initialize the queue */
if (!blk_init_allocated_queue(md->queue, dm_old_request_fn, NULL))
return -EINVAL;
@@ -854,11 +856,12 @@ int dm_old_init_request_queue(struct mapped_device *md)
/* Initialize the request-based DM worker thread */
init_kthread_worker(&md->kworker);
- md->kworker_task = kthread_run(kthread_worker_fn, &md->kworker,
- "kdmwork-%s", dm_device_name(md));
- if (IS_ERR(md->kworker_task))
- return PTR_ERR(md->kworker_task);
+ task = kthread_run(kthread_worker_fn, &md->kworker, "kdmwork-%s",
+ dm_device_name(md));
+ if (IS_ERR(task))
+ return PTR_ERR(task);
+ md->kworker_task = task;
elv_register_queue(md->queue);
return 0;
--
2.8.0.rc3.226.g39d4020