[syzbot] possible deadlock in rds_tcp_reset_callbacks

[syzbot <syzbot+78c55c7bc6f66e53dce2@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    8755ae45a9e8 Add linux-next specific files for 20220819
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=107cf485080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ead6107a3bbe3c62
dashboard link: https://syzkaller.appspot.com/bug?extid=78c55c7bc6f66e53dce2
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12e678cb080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f68e5b080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78c55c7bc6f66e53dce2@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc1-next-20220819-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:3/46 is trying to acquire lock:
ffff888027dc40e8 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}, at: __flush_work+0xdd/0xae0 kernel/workqueue.c:3066

but task is already holding lock:
ffff88807e18da70 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1712 [inline]
ffff88807e18da70 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: rds_tcp_reset_callbacks+0x1bf/0x4d0 net/rds/tcp.c:169

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (k-sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x36/0xf0 net/core/sock.c:3391
       lock_sock include/net/sock.h:1712 [inline]
       tcp_sock_set_cork+0x16/0x90 net/ipv4/tcp.c:3328
       rds_send_xmit+0x386/0x2540 net/rds/send.c:194
       rds_send_worker+0x92/0x2e0 net/rds/threads.c:200
       process_one_work+0x991/0x1610 kernel/workqueue.c:2289
       worker_thread+0x665/0x1080 kernel/workqueue.c:2436
       kthread+0x2e4/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #0 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3829 [inline]
       __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
       lock_acquire kernel/locking/lockdep.c:5666 [inline]
       lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
       __flush_work+0x105/0xae0 kernel/workqueue.c:3069
       __cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
       rds_tcp_reset_callbacks+0x1cb/0x4d0 net/rds/tcp.c:171
       rds_tcp_accept_one+0x9d5/0xd10 net/rds/tcp_listen.c:203
       rds_tcp_accept_worker+0x55/0x80 net/rds/tcp.c:529
       process_one_work+0x991/0x1610 kernel/workqueue.c:2289
       worker_thread+0x665/0x1080 kernel/workqueue.c:2436
       kthread+0x2e4/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(k-sk_lock-AF_INET6);
                               lock((work_completion)(&(&cp->cp_send_w)->work));
                               lock(k-sk_lock-AF_INET6);
  lock((work_completion)(&(&cp->cp_send_w)->work));

 *** DEADLOCK ***

4 locks held by kworker/u4:3/46:
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline]
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline]
 #0: ffff8880275f7938 ((wq_completion)krdsd){+.+.}-{0:0}, at: process_one_work+0x87a/0x1610 kernel/workqueue.c:2260
 #1: ffffc90000b77da8 ((work_completion)(&rtn->rds_tcp_accept_w)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264
 #2: ffff8880733c4088 (&tc->t_conn_path_lock){+.+.}-{3:3}, at: rds_tcp_accept_one+0x892/0xd10 net/rds/tcp_listen.c:195
 #3: ffff88807e18da70 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1712 [inline]
 #3: ffff88807e18da70 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: rds_tcp_reset_callbacks+0x1bf/0x4d0 net/rds/tcp.c:169

stack backtrace:
CPU: 1 PID: 46 Comm: kworker/u4:3 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0
kworker/u4:3[46] cmdline: ��a�����\x01
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Workqueue: krdsd rds_tcp_accept_worker
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:122 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:140
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3829 [inline]
 __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
 lock_acquire kernel/locking/lockdep.c:5666 [inline]
 lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
 __flush_work+0x105/0xae0 kernel/workqueue.c:3069
 __cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
 rds_tcp_reset_callbacks+0x1cb/0x4d0 net/rds/tcp.c:171
 rds_tcp_accept_one+0x9d5/0xd10 net/rds/tcp_listen.c:203
 rds_tcp_accept_worker+0x55/0x80 net/rds/tcp.c:529
 process_one_work+0x991/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>


---
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