Re: [syzbot] WARNING: suspicious RCU usage in nf_ct_iterate_cleanup (2)

[Dmitry Vyukov]

On Wed, May 5, 2021 at 9:51 AM syzbot
<syzbot+86efe6206c1373c8a7cc@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=120f2da3d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe
> dashboard link: https://syzkaller.appspot.com/bug?extid=86efe6206c1373c8a7cc
>
> 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:
> Reported-by: syzbot+86efe6206c1373c8a7cc@xxxxxxxxxxxxxxxxxxxxxxxxx

#syz fix: rcu: Reject RCU_LOCKDEP_WARN() false positives

> =============================
> WARNING: suspicious RCU usage
> 5.12.0-syzkaller #0 Not tainted
> -----------------------------
> kernel/sched/core.c:8304 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
> 3 locks held by kworker/u4:7/11790:
>  #0:
> ffff888011e93138
>  (
> (wq_completion)netns
> ){+.+.}-{0:0}
> , at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
> , at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
> , at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
> , at: set_work_data kernel/workqueue.c:616 [inline]
> , at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
> , at: process_one_work+0x871/0x1600 kernel/workqueue.c:2246
>  #1:
> ffffc90002377da8
>  (
> net_cleanup_work
> ){+.+.}-{0:0}
> , at: process_one_work+0x8a5/0x1600 kernel/workqueue.c:2250
>  #2:
> ffffffff8d672190
>  (
> pernet_ops_rwsem
> ){++++}-{3:3}
> , at: cleanup_net+0x9b/0xb10 net/core/net_namespace.c:557
>
> stack backtrace:
> CPU: 1 PID: 11790 Comm: kworker/u4:7 Not tainted 5.12.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: netns cleanup_net
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8304
>  get_next_corpse net/netfilter/nf_conntrack_core.c:2223 [inline]
>  nf_ct_iterate_cleanup+0x16d/0x450 net/netfilter/nf_conntrack_core.c:2245
>  nf_conntrack_cleanup_net_list+0x81/0x250 net/netfilter/nf_conntrack_core.c:2432
>  ops_exit_list+0x10d/0x160 net/core/net_namespace.c:178
>  cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:595
>  process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
>  worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
>  kthread+0x3b1/0x4a0 kernel/kthread.c:313
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
>
>
> ---
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>
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