linux-kernel - [syzbot] possible deadlock in tcp_sock_set

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Date:   Wed, 12 Oct 2022 07:03:39 -0700
From:   syzbot <syzbot+c4b21407c3b1dc66ee65@...kaller.appspotmail.com>
To:     bpf@...r.kernel.org, davem@...emloft.net, dsahern@...nel.org,
        edumazet@...gle.com, kuba@...nel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
        netdev@...r.kernel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com, trix@...hat.com,
        yoshfuji@...ux-ipv6.org
Subject: [syzbot] possible deadlock in tcp_sock_set_cork

Hello,

syzbot found the following issue on:

HEAD commit:    a5088ee7251e Merge tag 'thermal-6.1-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17c929b8880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=201ae572239e648
dashboard link: https://syzkaller.appspot.com/bug?extid=c4b21407c3b1dc66ee65
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/26341f70ccb8/disk-a5088ee7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca8a6f6b0303/vmlinux-a5088ee7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c4b21407c3b1dc66ee65@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.0.0-syzkaller-00372-ga5088ee7251e #0 Not tainted
------------------------------------------------------
kworker/u4:27/14295 is trying to acquire lock:
ffff888022948fb0 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1712 [inline]
ffff888022948fb0 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sock_set_cork+0x16/0x90 net/ipv4/tcp.c:3337

but task is already holding lock:
ffffc90004a4fda8 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}:
       __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

-> #0 (k-sk_lock-AF_INET6){+.+.}-{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
       lock_sock_nested+0x36/0xf0 net/core/sock.c:3393
       lock_sock include/net/sock.h:1712 [inline]
       tcp_sock_set_cork+0x16/0x90 net/ipv4/tcp.c:3337
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

2 locks held by kworker/u4:27/14295:
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline]
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline]
 #0: ffff888027f19938 ((wq_completion)krdsd){+.+.}-{0:0}, at: process_one_work+0x87a/0x1610 kernel/workqueue.c:2260
 #1: ffffc90004a4fda8 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

stack backtrace:
CPU: 0 PID: 14295 Comm: kworker/u4:27 Not tainted 6.0.0-syzkaller-00372-ga5088ee7251e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Workqueue: krdsd rds_send_worker
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 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
 lock_sock_nested+0x36/0xf0 net/core/sock.c:3393
 lock_sock include/net/sock.h:1712 [inline]
 tcp_sock_set_cork+0x16/0x90 net/ipv4/tcp.c:3337
 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
 </TASK>


---
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