syzbot

======================================================
WARNING: possible circular locking dependency detected
6.8.0-rc5-syzkaller-00029-g39133352cbed #0 Not tainted
------------------------------------------------------
syz-executor.2/8207 is trying to acquire lock:
ffff88802f68dd80 (&u->iolock){+.+.}-{3:3}, at: unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789

but task is already holding lock:
ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline]
ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_UNIX){+.+.}-{0:0}:
       lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
       lock_sock_nested+0x48/0x100 net/core/sock.c:3524
       lock_sock include/net/sock.h:1691 [inline]
       __unix_dgram_recvmsg+0x1275/0x12c0 net/unix/af_unix.c:2415
       sock_recvmsg_nosec+0x18e/0x1d0 net/socket.c:1046
       ____sys_recvmsg+0x3c0/0x470 net/socket.c:2801
       ___sys_recvmsg net/socket.c:2845 [inline]
       do_recvmmsg+0x474/0xae0 net/socket.c:2939
       __sys_recvmmsg net/socket.c:3018 [inline]
       __do_sys_recvmmsg net/socket.c:3041 [inline]
       __se_sys_recvmmsg net/socket.c:3034 [inline]
       __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3034
       do_syscall_64+0xf9/0x240
       entry_SYSCALL_64_after_hwframe+0x6f/0x77

-> #0 (&u->iolock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789
       sk_setsockopt+0x207e/0x3360
       do_sock_setsockopt+0x2fb/0x720 net/socket.c:2307
       __sys_setsockopt+0x1ad/0x250 net/socket.c:2334
       __do_sys_setsockopt net/socket.c:2343 [inline]
       __se_sys_setsockopt net/socket.c:2340 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
       do_syscall_64+0xf9/0x240
       entry_SYSCALL_64_after_hwframe+0x6f/0x77

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_UNIX);
                               lock(&u->iolock);
                               lock(sk_lock-AF_UNIX);
  lock(&u->iolock);

 *** DEADLOCK ***

1 lock held by syz-executor.2/8207:
 #0: ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline]
 #0: ffff88802f68d930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193

stack backtrace:
CPU: 0 PID: 8207 Comm: syz-executor.2 Not tainted 6.8.0-rc5-syzkaller-00029-g39133352cbed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789
 sk_setsockopt+0x207e/0x3360
 do_sock_setsockopt+0x2fb/0x720 net/socket.c:2307
 __sys_setsockopt+0x1ad/0x250 net/socket.c:2334
 __do_sys_setsockopt net/socket.c:2343 [inline]
 __se_sys_setsockopt net/socket.c:2340 [inline]
 __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f481547dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f48161df0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f48155abf80 RCX: 00007f481547dda9
RDX: 000000000000002a RSI: 0000000000000001 RDI: 0000000000000004
RBP: 00007f48154ca47a R08: 0000000000000004 R09: 0000000000000000
R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f48155abf80 R15: 00007ffe39912188
 </TASK>