possible deadlock in ip_set_nfnl_get_byindex

Status: upstream: reported on 2026/03/23 18:39
Reported-by: syzbot+d6e76f33e4d273c880e8@syzkaller.appspotmail.com
First crash: 204d, last: 2h30m
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ip_set_nfnl_get_byindex netfilter 4 21 237d 335d 0/29 closed as dup on 2026/01/05 09:18
linux-6.1 possible deadlock in ip_set_nfnl_get_byindex 4 96 1h32m 207d 0/3 upstream: reported on 2026/03/21 00:14

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.3768/17547 is trying to acquire lock:
ffffffff984c6c18 (nfnl_subsys_ipset){+.+.}-{3:3}, at: ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:916

but task is already holding lock:
ffff8880263870b8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid+0x3b/0x100 net/netfilter/nf_tables_api.c:10806

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nft_net->commit_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       nf_tables_dumpreset_obj+0x72/0xa0 net/netfilter/nf_tables_api.c:7950
       netlink_dump+0x738/0xec0 net/netlink/af_netlink.c:2269
       __netlink_dump_start+0x57c/0x7a0 net/netlink/af_netlink.c:2377
       netlink_dump_start include/linux/netlink.h:338 [inline]
       nft_netlink_dump_start_rcu+0xdb/0x1a0 net/netfilter/nf_tables_api.c:1074
       nf_tables_getobj_reset+0x1e1/0x620 net/netfilter/nf_tables_api.c:8085
       nfnetlink_rcv_msg+0x89c/0x1290 net/netfilter/nfnetlink.c:290
       netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
       nfnetlink_rcv+0x2c9/0x2490 net/netfilter/nfnetlink.c:659
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg net/socket.c:745 [inline]
       ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
       ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2687 [inline]
       __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (nlk_cb_mutex-NETFILTER){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       __netlink_dump_start+0xf4/0x7a0 net/netlink/af_netlink.c:2341
       netlink_dump_start include/linux/netlink.h:338 [inline]
       ip_set_dump+0x15c/0x1f0 net/netfilter/ipset/ip_set_core.c:1730
       nfnetlink_rcv_msg+0xcaf/0x1290 net/netfilter/nfnetlink.c:302
       netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
       nfnetlink_rcv+0x2c9/0x2490 net/netfilter/nfnetlink.c:659
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg net/socket.c:745 [inline]
       ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
       ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2687 [inline]
       __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (nfnl_subsys_ipset){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3162 [inline]
       check_prevs_add kernel/locking/lockdep.c:3281 [inline]
       validate_chain kernel/locking/lockdep.c:3897 [inline]
       __lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:916
       set_target_v1_checkentry+0x8c/0x4f0 net/netfilter/xt_set.c:313
       xt_check_target+0x4a1/0xbf0 net/netfilter/x_tables.c:1061
       nft_target_init+0x694/0xa00 net/netfilter/nft_compat.c:268
       nf_tables_newexpr net/netfilter/nf_tables_api.c:3257 [inline]
       nf_tables_newrule+0x176e/0x2870 net/netfilter/nf_tables_api.c:4089
       nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
       nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
       nfnetlink_rcv+0x1133/0x2490 net/netfilter/nfnetlink.c:657
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg net/socket.c:745 [inline]
       ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
       ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2687 [inline]
       __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

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.0.3768/17547:
 #0: ffff8880263870b8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid+0x3b/0x100 net/netfilter/nf_tables_api.c:10806

stack backtrace:
CPU: 1 PID: 17547 Comm: syz.0.3768 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2215
 check_prev_add kernel/locking/lockdep.c:3162 [inline]
 check_prevs_add kernel/locking/lockdep.c:3281 [inline]
 validate_chain kernel/locking/lockdep.c:3897 [inline]
 __lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
 ip_set_nfnl_get_byindex+0x67/0x230 net/netfilter/ipset/ip_set_core.c:916
 set_target_v1_checkentry+0x8c/0x4f0 net/netfilter/xt_set.c:313
 xt_check_target+0x4a1/0xbf0 net/netfilter/x_tables.c:1061
 nft_target_init+0x694/0xa00 net/netfilter/nft_compat.c:268
 nf_tables_newexpr net/netfilter/nf_tables_api.c:3257 [inline]
 nf_tables_newrule+0x176e/0x2870 net/netfilter/nf_tables_api.c:4089
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
 nfnetlink_rcv+0x1133/0x2490 net/netfilter/nfnetlink.c:657
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f317fd9e2d9
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:00007f3180c0e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f3180025fa0 RCX: 00007f317fd9e2d9
RDX: 0000000000000800 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007f317fe35888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3180026038 R14: 00007f3180025fa0 R15: 00007fff9edba9c8
 </TASK>

Crashes (101):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/14 07:20 linux-6.6.y a91a6aa9253c 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/14 07:20 linux-6.6.y a91a6aa9253c 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/14 02:19 linux-6.6.y a91a6aa9253c 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/11 15:33 linux-6.6.y a91a6aa9253c 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/05 12:27 linux-6.6.y a91a6aa9253c af63e995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/03 17:24 linux-6.6.y a91a6aa9253c 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/03 16:21 linux-6.6.y a91a6aa9253c 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/02 18:23 linux-6.6.y 79643295eba1 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/10/02 02:49 linux-6.6.y 79643295eba1 6d32eb1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/30 11:25 linux-6.6.y 79643295eba1 7808aef4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/30 02:55 linux-6.6.y 79643295eba1 328436b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/25 03:25 linux-6.6.y 79643295eba1 f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/24 20:20 linux-6.6.y 79643295eba1 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/22 21:14 linux-6.6.y 79643295eba1 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/09 18:00 linux-6.6.y 8b73de7da85f 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/09 05:09 linux-6.6.y 8b73de7da85f 8387c273 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/08 15:59 linux-6.6.y 8b73de7da85f 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/07 12:48 linux-6.6.y 8b73de7da85f 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/06 04:34 linux-6.6.y 8b73de7da85f 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/04 23:40 linux-6.6.y 8b73de7da85f 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/04 10:48 linux-6.6.y 8b73de7da85f f65209a4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/03 21:46 linux-6.6.y 8b73de7da85f 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/02 16:07 linux-6.6.y 8b73de7da85f 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/09/01 11:52 linux-6.6.y a4a971135a2f 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/08/28 21:42 linux-6.6.y a4a971135a2f 2f52988a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/08/23 16:08 linux-6.6.y dc6160265ffc 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/08/15 00:58 linux-6.6.y d27334b2888c 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/08/10 19:33 linux-6.6.y d27334b2888c 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/08/03 11:12 linux-6.6.y aa0e49877a2e 6b7c9f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/29 17:39 linux-6.6.y ae068b676196 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/28 14:09 linux-6.6.y c5596480c50e edc8a875 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/27 21:53 linux-6.6.y c5596480c50e aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/27 18:40 linux-6.6.y c5596480c50e aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/24 05:42 linux-6.6.y da47cbc25466 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/24 00:59 linux-6.6.y da47cbc25466 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/23 18:34 linux-6.6.y da47cbc25466 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/22 04:50 linux-6.6.y da47cbc25466 b561ce9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/22 03:03 linux-6.6.y da47cbc25466 b561ce9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/20 21:26 linux-6.6.y da47cbc25466 de6a700d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/19 16:47 linux-6.6.y da47cbc25466 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/10 05:16 linux-6.6.y da47cbc25466 4167ee25 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/07/10 05:16 linux-6.6.y da47cbc25466 4167ee25 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
2026/03/23 18:38 linux-6.6.y 4fc00fe35d46 4933dba2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ip_set_nfnl_get_byindex
* Struck through repros no longer work on HEAD.