[syzbot] possible deadlock in ip_mc_drop_socket

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb6ec87f net: dsa: Fix type was not set for devlink port
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=12dd978ad00000
kernel config: https://syzkaller.appspot.com/x/.config?x=daeff30c2474a60f
dashboard link: https://syzkaller.appspot.com/bug?extid=35ace9909754e04618b9

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+35ace9...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/31420 is trying to acquire lock:
ffffffff8d66b1a8 (rtnl_mutex){+.+.}-{3:3}, at: ip_mc_drop_socket+0x89/0x260 net/ipv4/igmp.c:2671

but task is already holding lock:
ffff888059d6c4a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1600 [inline]
ffff888059d6c4a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_release+0x55/0x120 net/mptcp/protocol.c:3431

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_INET){+.+.}-{0:0}:
lock_sock_nested+0xca/0x120 net/core/sock.c:3071
lock_sock include/net/sock.h:1600 [inline]
do_ip_setsockopt net/ipv4/ip_sockglue.c:945 [inline]
ip_setsockopt+0x1d2/0x3a00 net/ipv4/ip_sockglue.c:1423
udp_setsockopt+0x76/0xc0 net/ipv4/udp.c:2719
__sys_setsockopt+0x2db/0x610 net/socket.c:2117
__do_sys_setsockopt net/socket.c:2128 [inline]
__se_sys_setsockopt net/socket.c:2125 [inline]
__x64_sys_setsockopt+0xba/0x150 net/socket.c:2125
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (rtnl_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:2936 [inline]
check_prevs_add kernel/locking/lockdep.c:3059 [inline]
validate_chain kernel/locking/lockdep.c:3674 [inline]
__lock_acquire+0x2b14/0x54c0 kernel/locking/lockdep.c:4900
lock_acquire kernel/locking/lockdep.c:5510 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
__mutex_lock_common kernel/locking/mutex.c:949 [inline]
__mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096
ip_mc_drop_socket+0x89/0x260 net/ipv4/igmp.c:2671
mptcp_release+0xab/0x120 net/mptcp/protocol.c:3438
__sock_release+0xcd/0x280 net/socket.c:599
sock_close+0x18/0x20 net/socket.c:1258
__fput+0x288/0x920 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:140
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sk_lock-AF_INET);
lock(rtnl_mutex);
lock(sk_lock-AF_INET);
lock(rtnl_mutex);

*** DEADLOCK ***

2 locks held by syz-executor.4/31420:
#0: ffff88802ee8e190 (&sb->s_type->i_mutex_key#13){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:775 [inline]
#0: ffff88802ee8e190 (&sb->s_type->i_mutex_key#13){+.+.}-{3:3}, at: __sock_release+0x86/0x280 net/socket.c:598
#1: ffff888059d6c4a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1600 [inline]
#1: ffff888059d6c4a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_release+0x55/0x120 net/mptcp/protocol.c:3431

stack backtrace:
CPU: 0 PID: 31420 Comm: syz-executor.4 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2127
check_prev_add kernel/locking/lockdep.c:2936 [inline]
check_prevs_add kernel/locking/lockdep.c:3059 [inline]
validate_chain kernel/locking/lockdep.c:3674 [inline]
__lock_acquire+0x2b14/0x54c0 kernel/locking/lockdep.c:4900
lock_acquire kernel/locking/lockdep.c:5510 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
__mutex_lock_common kernel/locking/mutex.c:949 [inline]
__mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096
ip_mc_drop_socket+0x89/0x260 net/ipv4/igmp.c:2671
mptcp_release+0xab/0x120 net/mptcp/protocol.c:3438
__sock_release+0xcd/0x280 net/socket.c:599
sock_close+0x18/0x20 net/socket.c:1258
__fput+0x288/0x920 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:140
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x41926b
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:00007ffc0696dff0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 000000000041926b
RDX: 0000000000570b58 RSI: 000000000d1147dc RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b31a25db8
R10: 00007ffc0696e0e0 R11: 0000000000000293 R12: 0000000000094f5f
R13: 00000000000003e8 R14: 000000000056bf60 R15: 0000000000094f24


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.