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Thu, 02 Jul 2026 00:08:38 -0700 (PDT) Date: Thu, 02 Jul 2026 00:08:38 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a460e76.6912059f.e0473.0001.GAE@google.com> Subject: [moderation/CI] Re: net: Support per-netns device unregistration From: syzbot ci To: syzkaller-upstream-moderation@googlegroups.com Cc: syzbot@lists.linux.dev Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] net: Support per-netns device unregistration https://lore.kernel.org/all/20260701214334.266991-1-kuniyu@google.com * [PATCH v1 net-next 01/14] rtnetlink: Lock sock_net(skb->sk) in rtnl_newlink(). * [PATCH v1 net-next 02/14] rtnetlink: Call unregister_netdevice_many() only once in rtnl_link_unregister(). * [PATCH v1 net-next 03/14] rtnetlink: Add per-netns rtnl_work. * [PATCH v1 net-next 04/14] net: Wrap default_device_exit_net() with __rtnl_net_lock(). * [PATCH v1 net-next 05/14] net: Hold __rtnl_net_lock() in netdev_wait_allrefs_any(). * [PATCH v1 net-next 06/14] net: Add per-netns netdev unregistration infra. * [PATCH v1 net-next 07/14] net: Call unregister_netdevice_many() per netns. * [PATCH v1 net-next 08/14] veth: Support per-netns device unregistration. * [PATCH v1 net-next 09/14] bareudp: Protect bareudp_list with mutex. * [PATCH v1 net-next 10/14] bareudp: Support per-netns netdev unregistration. * [PATCH v1 net-next 11/14] ipvlan: Convert ipvl_port.count to refcount_t. * [PATCH v1 net-next 12/14] ipvlan: Synchronise ipvlan_init() and ipvlan_uninit() for the same lower dev. * [PATCH v1 net-next 13/14] ipvlan: Protect ipvl_port.ipvlans with mutex. * [PATCH v1 net-next 14/14] ipvlan: Support per-netns netdev unregistration. and found the following issue: possible deadlock in __dev_change_net_namespace Full report is available here: https://ci.syzbot.org/series/a744b257-d741-4780-8a53-f156b2a7afc9 *** possible deadlock in __dev_change_net_namespace tree: net-next URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git base: d6e81529749190123aa0040626c7e5dbc20fdc9a arch: amd64 compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6 config: https://ci.syzbot.org/builds/243cd0ec-28f9-4d21-8f16-3d2fbad8388d/config syz repro: https://ci.syzbot.org/findings/a8a0740d-fdec-4a20-9aa5-7cb955707913/syz_repro veth0_macvtap: left promiscuous mode ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.1.18/5814 is trying to acquire lock: ffffffff9a9b0418 (&net->dev_unreg_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffffffff9a9b0418 (&net->dev_unreg_lock){+.+.}-{3:3}, at: unregister_netdevice_move_net net/core/dev.c:-1 [inline] ffffffff9a9b0418 (&net->dev_unreg_lock){+.+.}-{3:3}, at: __dev_change_net_namespace+0x1479/0x2200 net/core/dev.c:12768 but task is already holding lock: ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: unregister_netdevice_move_net net/core/dev.c:-1 [inline] ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: __dev_change_net_namespace+0x146a/0x2200 net/core/dev.c:12768 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&net->dev_unreg_lock); lock(&net->dev_unreg_lock); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by syz.1.18/5814: #0: ffffffff8fdeb0c0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff8fdeb0c0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock+0x2a/0x2b0 net/core/rtnetlink.c:366 #1: ffffffff9a9b0380 (&net->rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock+0x76/0x2b0 net/core/rtnetlink.c:369 #2: ffff88810b6cf840 (&net->rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock+0xbf/0x2b0 net/core/rtnetlink.c:369 #3: ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] #3: ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: unregister_netdevice_move_net net/core/dev.c:-1 [inline] #3: ffff88810b6cf8d8 (&net->dev_unreg_lock){+.+.}-{3:3}, at: __dev_change_net_namespace+0x146a/0x2200 net/core/dev.c:12768 stack backtrace: CPU: 0 UID: 0 PID: 5814 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: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x24df/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:158 spin_lock include/linux/spinlock.h:342 [inline] unregister_netdevice_move_net net/core/dev.c:-1 [inline] __dev_change_net_namespace+0x1479/0x2200 net/core/dev.c:12768 do_setlink+0x2d1/0x4670 net/core/rtnetlink.c:3148 rtnl_changelink net/core/rtnetlink.c:3880 [inline] __rtnl_newlink net/core/rtnetlink.c:4053 [inline] rtnl_newlink+0x1612/0x1b50 net/core/rtnetlink.c:4192 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7109 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bb/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:775 __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2684 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738 __sys_sendmsg net/socket.c:2770 [inline] __do_sys_sendmsg net/socket.c:2775 [inline] __se_sys_sendmsg net/socket.c:2773 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fbdc639ce59 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:00007fbdc59fe028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fbdc6615fa0 RCX: 00007fbdc639ce59 RDX: 0000000000000000 RSI: 0000200000000740 RDI: 0000000000000003 RBP: 00007fbdc6432e6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fbdc6616038 R14: 00007fbdc6615fa0 R15: 00007ffd94dcb1f8 syz.1.18 (5814) used greatest stack depth: 19864 bytes left *** 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. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com. To test a patch for this bug, please reply with `#syz test` (should be on a separate line). The patch should be attached to the email. Note: arguments like custom git repos and branches are not supported. The email will later be sent to: [andrew@lunn.ch davem@davemloft.net edumazet@google.com horms@kernel.org kuba@kernel.org kuni1840@gmail.com kuniyu@google.com netdev@vger.kernel.org pabeni@redhat.com] If the report looks fine to you, reply with: #syz upstream If the report is a false positive, reply with #syz invalid