[syzbot ci] Re: xsk: Fix circular locking dependency between &net->xdp.lock, &xs->mutex, and netdev_lock_ops
From: syzbot ci <hidden>
Date: 2026-09-15 14:50:57
Also in:
bpf, lkml, syzbot
syzbot ci has tested the following series [v6] xsk: Fix circular locking dependency between &net->xdp.lock, &xs->mutex, and netdev_lock_ops https://lore.kernel.org/all/20260915081023.7433-1-ahemadkhawar123@gmail.com (local) * [PATCH bpf-next v6] xsk: Fix circular locking dependency between &net->xdp.lock, &xs->mutex, and netdev_lock_ops and found the following issue: possible deadlock in xp_clear_dev Full report is available here: https://ci.syzbot.org/series/fd897794-4f0d-45f4-8e63-bcb526e0b175 *** possible deadlock in xp_clear_dev tree: bpf-next URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next.git base: b0ca562e0d05cf7afedcfa71c9aed180b72bcc97 arch: amd64 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/d5521b86-a0b8-4ffc-ada4-91f534b028bc/config syz repro: https://ci.syzbot.org/findings/6aa094b3-5f39-460c-b0f7-709bbf72644c/syz_repro netlink: 14 bytes leftover after parsing attributes in process `syz.1.18'. ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.18/5842 is trying to acquire lock: ffff8881793b4e70 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2861 [inline] ffff8881793b4e70 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline] ffff8881793b4e70 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: xp_clear_dev+0x13b/0x340 net/xdp/xsk_buff_pool.c:297 but task is already holding lock: ffff8881bd5ca6b8 (&xs->mutex){+.+.}-{4:4}, at: xsk_notifier+0xcd/0x230 net/xdp/xsk.c:2114 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&xs->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 xsk_bind+0x297/0x13f0 net/xdp/xsk.c:1620 __sys_bind_socket net/socket.c:1945 [inline] __sys_bind+0x2e3/0x410 net/socket.c:1976 __do_sys_bind net/socket.c:1981 [inline] __se_sys_bind net/socket.c:1979 [inline] __x64_sys_bind+0x7a/0x90 net/socket.c:1979 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&dev_instance_lock_key#3){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 netdev_lock include/linux/netdevice.h:2861 [inline] netdev_lock_ops include/net/netdev_lock.h:42 [inline] xp_clear_dev+0x13b/0x340 net/xdp/xsk_buff_pool.c:297 xsk_notifier+0x1a1/0x230 net/xdp/xsk.c:2123 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline] call_netdevice_notifiers net/core/dev.c:2327 [inline] unregister_netdevice_many_notify+0x17f9/0x2140 net/core/dev.c:12518 rtnl_delete_link net/core/rtnetlink.c:3652 [inline] rtnl_dellink+0x5be/0x810 net/core/rtnetlink.c:3694 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7132 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&xs->mutex); lock(&dev_instance_lock_key#3); lock(&xs->mutex); lock(&dev_instance_lock_key#3); *** DEADLOCK *** locks held by syz.1.18/5842: 3, last CPU#0: #0: ffffffff90036ac0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff90036ac0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:134 [inline] #0: ffffffff90036ac0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dellink+0x41b/0x810 net/core/rtnetlink.c:3686 #1: ffff88810e3ac750 (&net->xdp.lock){+.+.}-{4:4}, at: xsk_notifier+0x89/0x230 net/xdp/xsk.c:2110 #2: ffff8881bd5ca6b8 (&xs->mutex){+.+.}-{4:4}, at: xsk_notifier+0xcd/0x230 net/xdp/xsk.c:2114 stack backtrace: CPU: 0 UID: 0 PID: 5842 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2059 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2191 check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 netdev_lock include/linux/netdevice.h:2861 [inline] netdev_lock_ops include/net/netdev_lock.h:42 [inline] xp_clear_dev+0x13b/0x340 net/xdp/xsk_buff_pool.c:297 xsk_notifier+0x1a1/0x230 net/xdp/xsk.c:2123 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline] call_netdevice_notifiers net/core/dev.c:2327 [inline] unregister_netdevice_many_notify+0x17f9/0x2140 net/core/dev.c:12518 rtnl_delete_link net/core/rtnetlink.c:3652 [inline] rtnl_dellink+0x5be/0x810 net/core/rtnetlink.c:3694 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7132 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f47db99e159 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:00007f47dc90c028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f47dbc25fa0 RCX: 00007f47db99e159 RDX: 0000000004048004 RSI: 00002000000001c0 RDI: 0000000000000005 RBP: 00007f47dba3503b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f47dbc26038 R14: 00007f47dbc25fa0 R15: 00007ffc72db97b8 </TASK> *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. 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