Subject: WARNING: suspicious RCU usage in tipc_udp_send_msg

From: syzbot <[email-masked]>
Date: Mon, 22 Jun 2020 09:37:11 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    67c20de3 net: Add MODULE_DESCRIPTION entries to network mo..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=16de7aed100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=45c80de7244166e1
dashboard link: https://syzkaller.appspot.com/bug?extid=7b0553cceace6d4a2b82
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

=============================
WARNING: suspicious RCU usage
5.8.0-rc1-syzkaller #0 Not tainted
-----------------------------
net/tipc/udp_media.c:241 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
2 locks held by kworker/1:17/1829:
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff8880a6986538 ((wq_completion)cryptd){+.+.}-{0:0}, at: process_one_work+0x844/0x1690 kernel/workqueue.c:2240
 #1: ffffc90008e57dc0 ((work_completion)(&cpu_queue->work)){+.+.}-{0:0}, at: process_one_work+0x878/0x1690 kernel/workqueue.c:2244

stack backtrace:
CPU: 1 PID: 1829 Comm: kworker/1:17 Not tainted 5.8.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: cryptd cryptd_queue_worker
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 tipc_udp_send_msg+0x3b1/0x480 net/tipc/udp_media.c:241
 tipc_aead_encrypt_done+0x204/0x3a0 net/tipc/crypto.c:761
 cryptd_aead_crypt+0xe8/0x1d0 crypto/cryptd.c:739
 cryptd_queue_worker+0x118/0x1b0 crypto/cryptd.c:181
 process_one_work+0x965/0x1690 kernel/workqueue.c:2269
 worker_thread+0x96/0xe10 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

---
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