[syzbot] possible deadlock in do_ipv6_setsockopt (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 75887e88 Merge branch '40GbE' of git://git.kernel.org/pub/..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1133dd06d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=daeff30c2474a60f
dashboard link: https://syzkaller.appspot.com/bug?extid=0eedf083894a053f17a5

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+0eedf0...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/11001 is trying to acquire lock:
ffff88805c53ef60 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1600 [inline]
ffff88805c53ef60 (sk_lock-AF_INET6){+.+.}-{0:0}, at: do_ipv6_setsockopt.constprop.0+0x31f/0x41f0 net/ipv6/ipv6_sockglue.c:418

but task is already holding lock:
ffffffff8d66b1a8 (rtnl_mutex){+.+.}-{3:3}, at: do_ipv6_setsockopt.constprop.0+0x315/0x41f0 net/ipv6/ipv6_sockglue.c:417

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (rtnl_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:949 [inline]
__mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096
ipv6_sock_mc_close+0xd7/0x110 net/ipv6/mcast.c:323
mptcp6_release+0xb9/0x130 net/mptcp/protocol.c:3558
__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

-> #0 (sk_lock-AF_INET6){+.+.}-{0:0}:
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
lock_sock_nested+0xca/0x120 net/core/sock.c:3071
lock_sock include/net/sock.h:1600 [inline]
do_ipv6_setsockopt.constprop.0+0x31f/0x41f0 net/ipv6/ipv6_sockglue.c:418
ipv6_setsockopt+0xd6/0x180 net/ipv6/ipv6_sockglue.c:1003
tcp_setsockopt+0x136/0x24a0 net/ipv4/tcp.c:3643
__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

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rtnl_mutex);
lock(sk_lock-AF_INET6);
lock(rtnl_mutex);
lock(sk_lock-AF_INET6);

*** DEADLOCK ***

1 lock held by syz-executor.0/11001:
#0: ffffffff8d66b1a8 (rtnl_mutex){+.+.}-{3:3}, at: do_ipv6_setsockopt.constprop.0+0x315/0x41f0 net/ipv6/ipv6_sockglue.c:417

stack backtrace:
CPU: 0 PID: 11001 Comm: syz-executor.0 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
lock_sock_nested+0xca/0x120 net/core/sock.c:3071
lock_sock include/net/sock.h:1600 [inline]
do_ipv6_setsockopt.constprop.0+0x31f/0x41f0 net/ipv6/ipv6_sockglue.c:418
ipv6_setsockopt+0xd6/0x180 net/ipv6/ipv6_sockglue.c:1003
tcp_setsockopt+0x136/0x24a0 net/ipv4/tcp.c:3643
__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
RIP: 0033:0x466459
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f67f5e8f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 000000000056c200 RCX: 0000000000466459
RDX: 000000000000002d RSI: 0000000000000029 RDI: 0000000000000006
RBP: 00000000004bf9fb R08: 0000000000000088 R09: 0000000000000000
R10: 0000000020000100 R11: 0000000000000246 R12: 000000000056c200
R13: 00007fff467656ef R14: 00007f67f5e8f300 R15: 0000000000022000


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[syzbot]

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