syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/4435 is trying to acquire lock:
ffff88807b5c0120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: inet_sk_diag_fill+0xf5e/0x1ca0 net/ipv4/inet_diag.c:342

but task is already holding lock:
ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:95 [inline]
ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: mptcp_diag_dump+0x917/0x12b0 net/mptcp/mptcp_diag.c:194

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&h->lhash2[i].lock){+.+.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
       spin_lock include/linux/spinlock.h:364 [inline]
       __inet_hash+0xe3/0x960 net/ipv4/inet_hashtables.c:617
       inet_csk_listen_start+0x22f/0x320 net/ipv4/inet_connection_sock.c:1115
       inet_listen+0x2e1/0x590 net/ipv4/af_inet.c:231
       __sys_listen+0x19d/0x220 net/socket.c:1763
       __do_sys_listen net/socket.c:1772 [inline]
       __se_sys_listen net/socket.c:1770 [inline]
       __x64_sys_listen+0x56/0x60 net/socket.c:1770
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (sk_lock-AF_INET6){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       lock_sock_fast include/net/sock.h:1776 [inline]
       mptcp_diag_get_info+0x1f2/0x9e0 net/mptcp/mptcp_diag.c:224
       inet_sk_diag_fill+0xf5e/0x1ca0 net/ipv4/inet_diag.c:342
       sk_diag_dump net/mptcp/mptcp_diag.c:24 [inline]
       mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:122 [inline]
       mptcp_diag_dump+0xce6/0x12b0 net/mptcp/mptcp_diag.c:194
       __inet_diag_dump+0x1f6/0x380 net/ipv4/inet_diag.c:1179
       netlink_dump+0x694/0xcf0 net/netlink/af_netlink.c:2283
       __netlink_dump_start+0x523/0x700 net/netlink/af_netlink.c:2386
       netlink_dump_start include/linux/netlink.h:258 [inline]
       inet_diag_handler_cmd+0x1d3/0x2b0 net/ipv4/inet_diag.c:1344
       sock_diag_rcv_msg+0x164/0x3e0 net/core/sock_diag.c:-1
       netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
       sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:276
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
       sock_sendmsg_nosec net/socket.c:706 [inline]
       __sock_sendmsg net/socket.c:718 [inline]
       sock_write_iter+0x2a6/0x3a0 net/socket.c:1089
       do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
       do_iter_write+0x205/0x7b0 fs/read_write.c:855
       vfs_writev fs/read_write.c:928 [inline]
       do_writev+0x281/0x480 fs/read_write.c:971
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&h->lhash2[i].lock);
                               lock(sk_lock-AF_INET6);
                               lock(&h->lhash2[i].lock);
  lock(sk_lock-AF_INET6);

 *** DEADLOCK ***

6 locks held by syz.0.17/4435:
 #0: ffffffff8d4466e8 (sock_diag_mutex){+.+.}-{3:3}, at: sock_diag_rcv+0x17/0x40 net/core/sock_diag.c:275
 #1: ffffffff8d4465a8 (sock_diag_table_mutex){+.+.}-{3:3}, at: __sock_diag_cmd net/core/sock_diag.c:229 [inline]
 #1: ffffffff8d4465a8 (sock_diag_table_mutex){+.+.}-{3:3}, at: sock_diag_rcv_msg+0x217/0x3e0 net/core/sock_diag.c:265
 #2: ffff8880732c3698 (nlk_cb_mutex-SOCK_DIAG){+.+.}-{3:3}, at: __netlink_dump_start+0x11f/0x700 net/netlink/af_netlink.c:2352
 #3: ffffffff8d520588 (inet_diag_table_mutex){+.+.}-{3:3}, at: inet_diag_lock_handler net/ipv4/inet_diag.c:63 [inline]
 #3: ffffffff8d520588 (inet_diag_table_mutex){+.+.}-{3:3}, at: __inet_diag_dump+0x181/0x380 net/ipv4/inet_diag.c:1177
 #4: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
 #5: ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #5: ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:95 [inline]
 #5: ffffc900018317b8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: mptcp_diag_dump+0x917/0x12b0 net/mptcp/mptcp_diag.c:194

stack backtrace:
CPU: 1 PID: 4435 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 lock_sock_fast include/net/sock.h:1776 [inline]
 mptcp_diag_get_info+0x1f2/0x9e0 net/mptcp/mptcp_diag.c:224
 inet_sk_diag_fill+0xf5e/0x1ca0 net/ipv4/inet_diag.c:342
 sk_diag_dump net/mptcp/mptcp_diag.c:24 [inline]
 mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:122 [inline]
 mptcp_diag_dump+0xce6/0x12b0 net/mptcp/mptcp_diag.c:194
 __inet_diag_dump+0x1f6/0x380 net/ipv4/inet_diag.c:1179
 netlink_dump+0x694/0xcf0 net/netlink/af_netlink.c:2283
 __netlink_dump_start+0x523/0x700 net/netlink/af_netlink.c:2386
 netlink_dump_start include/linux/netlink.h:258 [inline]
 inet_diag_handler_cmd+0x1d3/0x2b0 net/ipv4/inet_diag.c:1344
 sock_diag_rcv_msg+0x164/0x3e0 net/core/sock_diag.c:-1
 netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
 sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:276
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1089
 do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
 do_iter_write+0x205/0x7b0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_writev+0x281/0x480 fs/read_write.c:971
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe2570a9799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcf6ecf198 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007fe257322fa0 RCX: 00007fe2570a9799
RDX: 0000000000000001 RSI: 0000200000000280 RDI: 0000000000000004
RBP: 00007fe25713fc99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe257322fac R14: 00007fe257322fa0 R15: 00007fe257322fa0
 </TASK>
BUG: sleeping function called from invalid context at net/core/sock.c:3291
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 4435, name: syz.0.17
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 PID: 4435 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 ___might_sleep+0x493/0x610 kernel/sched/core.c:9658
 __lock_sock_fast+0x2f/0xe0 net/core/sock.c:3291
 lock_sock_fast include/net/sock.h:1778 [inline]
 mptcp_diag_get_info+0x1fe/0x9e0 net/mptcp/mptcp_diag.c:224
 inet_sk_diag_fill+0xf5e/0x1ca0 net/ipv4/inet_diag.c:342
 sk_diag_dump net/mptcp/mptcp_diag.c:24 [inline]
 mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:122 [inline]
 mptcp_diag_dump+0xce6/0x12b0 net/mptcp/mptcp_diag.c:194
 __inet_diag_dump+0x1f6/0x380 net/ipv4/inet_diag.c:1179
 netlink_dump+0x694/0xcf0 net/netlink/af_netlink.c:2283
 __netlink_dump_start+0x523/0x700 net/netlink/af_netlink.c:2386
 netlink_dump_start include/linux/netlink.h:258 [inline]
 inet_diag_handler_cmd+0x1d3/0x2b0 net/ipv4/inet_diag.c:1344
 sock_diag_rcv_msg+0x164/0x3e0 net/core/sock_diag.c:-1
 netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
 sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:276
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1089
 do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
 do_iter_write+0x205/0x7b0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_writev+0x281/0x480 fs/read_write.c:971
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe2570a9799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcf6ecf198 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007fe257322fa0 RCX: 00007fe2570a9799
RDX: 0000000000000001 RSI: 0000200000000280 RDI: 0000000000000004
RBP: 00007fe25713fc99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe257322fac R14: 00007fe257322fa0 R15: 00007fe257322fa0
 </TASK>