syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.1.1805/13248 is trying to acquire lock:
ffffffff99dcd2b8 (nfnl_subsys_ipset){+.+.}-{4:4}, at: ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:909

but task is already holding lock:
ffff888079ec60d8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x3b/0x100 net/netfilter/nf_tables_api.c:11558

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nft_net->commit_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
       nf_tables_dumpreset_set+0xc5/0x290 net/netfilter/nf_tables_api.c:6347
       netlink_dump+0x6e4/0xe90 net/netlink/af_netlink.c:2325
       __netlink_dump_start+0x5cb/0x7e0 net/netlink/af_netlink.c:2440
       netlink_dump_start include/linux/netlink.h:341 [inline]
       nft_netlink_dump_start_rcu+0xdb/0x1a0 net/netfilter/nf_tables_api.c:1309
       nf_tables_getsetelem_reset+0x2b2/0xa60 net/netfilter/nf_tables_api.c:6663
       nfnetlink_rcv_msg+0x80e/0x1130 net/netfilter/nfnetlink.c:290
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
       nfnetlink_rcv+0x282/0x2590 net/netfilter/nfnetlink.c:669
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:742
       ____sys_sendmsg+0x505/0x820 net/socket.c:2592
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (nlk_cb_mutex-NETFILTER){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
       __netlink_dump_start+0xfe/0x7e0 net/netlink/af_netlink.c:2404
       netlink_dump_start include/linux/netlink.h:341 [inline]
       ip_set_dump+0x13e/0x1c0 net/netfilter/ipset/ip_set_core.c:1717
       nfnetlink_rcv_msg+0xb4d/0x1130 net/netfilter/nfnetlink.c:302
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
       nfnetlink_rcv+0x282/0x2590 net/netfilter/nfnetlink.c:669
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:742
       ____sys_sendmsg+0x505/0x820 net/socket.c:2592
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (nfnl_subsys_ipset){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
       ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:909
       set_target_v1_checkentry+0x8c/0x500 net/netfilter/xt_set.c:313
       xt_check_target+0x3c3/0xa90 net/netfilter/x_tables.c:1038
       nft_target_init+0x672/0x9c0 net/netfilter/nft_compat.c:267
       nf_tables_newexpr net/netfilter/nf_tables_api.c:3550 [inline]
       nf_tables_newrule+0x1794/0x28a0 net/netfilter/nf_tables_api.c:4419
       nfnetlink_rcv_batch net/netfilter/nfnetlink.c:526 [inline]
       nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:649 [inline]
       nfnetlink_rcv+0x11d9/0x2590 net/netfilter/nfnetlink.c:667
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:742
       ____sys_sendmsg+0x505/0x820 net/socket.c:2592
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  nfnl_subsys_ipset --> nlk_cb_mutex-NETFILTER --> &nft_net->commit_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&nft_net->commit_mutex);
                               lock(nlk_cb_mutex-NETFILTER);
                               lock(&nft_net->commit_mutex);
  lock(nfnl_subsys_ipset);

 *** DEADLOCK ***

1 lock held by syz.1.1805/13248:
 #0: ffff888079ec60d8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x3b/0x100 net/netfilter/nf_tables_api.c:11558

stack backtrace:
CPU: 0 UID: 0 PID: 13248 Comm: syz.1.1805 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:614 [inline]
 __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
 ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:909
 set_target_v1_checkentry+0x8c/0x500 net/netfilter/xt_set.c:313
 xt_check_target+0x3c3/0xa90 net/netfilter/x_tables.c:1038
 nft_target_init+0x672/0x9c0 net/netfilter/nft_compat.c:267
 nf_tables_newexpr net/netfilter/nf_tables_api.c:3550 [inline]
 nf_tables_newrule+0x1794/0x28a0 net/netfilter/nf_tables_api.c:4419
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:526 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:649 [inline]
 nfnetlink_rcv+0x11d9/0x2590 net/netfilter/nfnetlink.c:667
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x505/0x820 net/socket.c:2592
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7b6bd8f749
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7b6cc37038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7b6bfe5fa0 RCX: 00007f7b6bd8f749
RDX: 0000000000000800 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 00007f7b6be13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7b6bfe6038 R14: 00007f7b6bfe5fa0 R15: 00007f7b6c10fa28
 </TASK>
Cannot find del_set index 27392 as target