======================================================
WARNING: possible circular locking dependency detected
4.14.172-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:2/28 is trying to acquire lock:
 (sk_lock-AF_INET){+.+.}, at: [<ffffffff85be8d8e>] do_strp_work net/strparser/strparser.c:415 [inline]
 (sk_lock-AF_INET){+.+.}, at: [<ffffffff85be8d8e>] strp_work+0x3e/0x100 net/strparser/strparser.c:434

but task is already holding lock:
 ((&strp->work)){+.+.}, at: [<ffffffff813b5861>] process_one_work+0x761/0x1540 kernel/workqueue.c:2089

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((&strp->work)){+.+.}:
       flush_work+0xae/0x780 kernel/workqueue.c:2887
       __cancel_work_timer+0x2d0/0x460 kernel/workqueue.c:2962
       strp_done+0x53/0xd0 net/strparser/strparser.c:519
       kcm_attach net/kcm/kcmsock.c:1429 [inline]
       kcm_attach_ioctl net/kcm/kcmsock.c:1490 [inline]
       kcm_ioctl+0x856/0x1010 net/kcm/kcmsock.c:1701
       sock_do_ioctl+0x5f/0xa0 net/socket.c:974
       sock_ioctl+0x28d/0x450 net/socket.c:1071
       vfs_ioctl fs/ioctl.c:46 [inline]
       file_ioctl fs/ioctl.c:500 [inline]
       do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
       SYSC_ioctl fs/ioctl.c:701 [inline]
       SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (sk_lock-AF_INET){+.+.}:
       lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994
       lock_sock_nested+0xb7/0x100 net/core/sock.c:2770
       do_strp_work net/strparser/strparser.c:415 [inline]
       strp_work+0x3e/0x100 net/strparser/strparser.c:434
       process_one_work+0x813/0x1540 kernel/workqueue.c:2114
       worker_thread+0x5d1/0x1070 kernel/workqueue.c:2248
       kthread+0x30d/0x420 kernel/kthread.c:232
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((&strp->work));
                               lock(sk_lock-AF_INET);
                               lock((&strp->work));
  lock(sk_lock-AF_INET);

 *** DEADLOCK ***

2 locks held by kworker/u4:2/28:
 #0:  ("%s""kstrp"){+.+.}, at: [<ffffffff813b5827>] work_static include/linux/workqueue.h:199 [inline]
 #0:  ("%s""kstrp"){+.+.}, at: [<ffffffff813b5827>] set_work_data kernel/workqueue.c:619 [inline]
 #0:  ("%s""kstrp"){+.+.}, at: [<ffffffff813b5827>] set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
 #0:  ("%s""kstrp"){+.+.}, at: [<ffffffff813b5827>] process_one_work+0x727/0x1540 kernel/workqueue.c:2085
 #1:  ((&strp->work)){+.+.}, at: [<ffffffff813b5861>] process_one_work+0x761/0x1540 kernel/workqueue.c:2089

stack backtrace:
CPU: 1 PID: 28 Comm: kworker/u4:2 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kstrp strp_work
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x13e/0x194 lib/dump_stack.c:58
 print_circular_bug.isra.0.cold+0x1c4/0x282 kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1901 [inline]
 check_prevs_add kernel/locking/lockdep.c:2018 [inline]
 validate_chain kernel/locking/lockdep.c:2460 [inline]
 __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487
 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994
 lock_sock_nested+0xb7/0x100 net/core/sock.c:2770
 do_strp_work net/strparser/strparser.c:415 [inline]
 strp_work+0x3e/0x100 net/strparser/strparser.c:434
 process_one_work+0x813/0x1540 kernel/workqueue.c:2114
 worker_thread+0x5d1/0x1070 kernel/workqueue.c:2248
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
nla_parse: 730 callbacks suppressed
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
nla_parse: 842 callbacks suppressed
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.2'.