netdevsim: avoid potential loop in nsim_dev_trap_report_work()

Many syzbot reports include the following trace [1]

If nsim_dev_trap_report_work() can not grab the mutex,
it should rearm itself at least one jiffie later.

[1]
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 32383 Comm: kworker/0:2 Not tainted 6.8.0-rc2-syzkaller-00031-g861c0981648f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Workqueue: events nsim_dev_trap_report_work
 RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:89 [inline]
 RIP: 0010:memory_is_nonzero mm/kasan/generic.c:104 [inline]
 RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:129 [inline]
 RIP: 0010:memory_is_poisoned mm/kasan/generic.c:161 [inline]
 RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
 RIP: 0010:kasan_check_range+0x101/0x190 mm/kasan/generic.c:189
Code: 07 49 39 d1 75 0a 45 3a 11 b8 01 00 00 00 7c 0b 44 89 c2 e8 21 ed ff ff 83 f0 01 5b 5d 41 5c c3 48 85 d2 74 4f 48 01 ea eb 09 <48> 83 c0 01 48 39 d0 74 41 80 38 00 74 f2 eb b6 41 bc 08 00 00 00
RSP: 0018:ffffc90012dcf998 EFLAGS: 00000046
RAX: fffffbfff258af1e RBX: fffffbfff258af1f RCX: ffffffff8168eda3
RDX: fffffbfff258af1f RSI: 0000000000000004 RDI: ffffffff92c578f0
RBP: fffffbfff258af1e R08: 0000000000000000 R09: fffffbfff258af1e
R10: ffffffff92c578f3 R11: ffffffff8acbcbc0 R12: 0000000000000002
R13: ffff88806db38400 R14: 1ffff920025b9f42 R15: ffffffff92c578e8
FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00994e078 CR3: 000000002c250000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
  instrument_atomic_read include/linux/instrumented.h:68 [inline]
  atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
  queued_spin_is_locked include/asm-generic/qspinlock.h:57 [inline]
  debug_spin_unlock kernel/locking/spinlock_debug.c:101 [inline]
  do_raw_spin_unlock+0x53/0x230 kernel/locking/spinlock_debug.c:141
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:150 [inline]
  _raw_spin_unlock_irqrestore+0x22/0x70 kernel/locking/spinlock.c:194
  debug_object_activate+0x349/0x540 lib/debugobjects.c:726
  debug_work_activate kernel/workqueue.c:578 [inline]
  insert_work+0x30/0x230 kernel/workqueue.c:1650
  __queue_work+0x62e/0x11d0 kernel/workqueue.c:1802
  __queue_delayed_work+0x1bf/0x270 kernel/workqueue.c:1953
  queue_delayed_work_on+0x106/0x130 kernel/workqueue.c:1989
  queue_delayed_work include/linux/workqueue.h:563 [inline]
  schedule_delayed_work include/linux/workqueue.h:677 [inline]
  nsim_dev_trap_report_work+0x9c0/0xc80 drivers/net/netdevsim/dev.c:842
  process_one_work+0x886/0x15d0 kernel/workqueue.c:2633
  process_scheduled_works kernel/workqueue.c:2706 [inline]
  worker_thread+0x8b9/0x1290 kernel/workqueue.c:2787
  kthread+0x2c6/0x3a0 kernel/kthread.c:388
  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
 </TASK>

Fixes: 012ec02 ("netdevsim: convert driver to use unlocked devlink API during init/fini")
Reported-by: syzbot <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Jiri Pirko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: edumazet

drivers/net/netdevsim/dev.c

@@ -835,14 +835,14 @@ static void nsim_dev_trap_report_work(struct work_struct *work)
 				      trap_report_dw.work);
 	nsim_dev = nsim_trap_data->nsim_dev;
 
-	/* For each running port and enabled packet trap, generate a UDP
-	 * packet with a random 5-tuple and report it.
-	 */
 	if (!devl_trylock(priv_to_devlink(nsim_dev))) {
-		schedule_delayed_work(&nsim_dev->trap_data->trap_report_dw, 0);
+		schedule_delayed_work(&nsim_dev->trap_data->trap_report_dw, 1);
 		return;
 	}
 
+	/* For each running port and enabled packet trap, generate a UDP
+	 * packet with a random 5-tuple and report it.
+	 */
 	list_for_each_entry(nsim_dev_port, &nsim_dev->port_list, list) {
 		if (!netif_running(nsim_dev_port->ns->netdev))
 			continue;