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Date:   Tue, 15 Dec 2020 02:24:11 -0800
From:   syzbot <>
Subject: WARNING: suspicious RCU usage in nf_ct_iterate_cleanup


syzbot found the following issue on:

HEAD commit:    33dc9614 Merge tag 'ktest-v5.10-rc6' of git://git.kernel.o..
git tree:       upstream
console output:
kernel config:
dashboard link:
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:

WARNING: suspicious RCU usage
5.10.0-rc7-syzkaller #0 Not tainted
kernel/sched/core.c:7270 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 0
2 locks held by kworker/1:8/18355:
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff888010063d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x821/0x15a0 kernel/workqueue.c:2243
 #1: ffffc90002a6fda8 ((work_completion)(&w->work)#2){+.+.}-{0:0}, at: process_one_work+0x854/0x15a0 kernel/workqueue.c:2247

stack backtrace:
CPU: 1 PID: 18355 Comm: kworker/1:8 Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events iterate_cleanup_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 ___might_sleep+0x220/0x2b0 kernel/sched/core.c:7270
 get_next_corpse net/netfilter/nf_conntrack_core.c:2222 [inline]
 nf_ct_iterate_cleanup+0x132/0x400 net/netfilter/nf_conntrack_core.c:2244
 nf_ct_iterate_cleanup_net net/netfilter/nf_conntrack_core.c:2329 [inline]
 nf_ct_iterate_cleanup_net+0x113/0x170 net/netfilter/nf_conntrack_core.c:2314
 iterate_cleanup_work+0x45/0x130 net/netfilter/nf_nat_masquerade.c:216
 process_one_work+0x933/0x15a0 kernel/workqueue.c:2272
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2418
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

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