bisecting fixing commit since 3d40d7117e353b84627c1e8c5ed9ae0b1237ef5c building syzkaller on 438e1227121e9d4bbca7b12b6e1b715524d512c2 testing commit 3d40d7117e353b84627c1e8c5ed9ae0b1237ef5c with gcc (GCC) 8.1.0 kernel signature: 78f5e43aed1f1301dcf580291a4b306b30f8026a68ac67ebe2352677851c0730 all runs: crashed: possible deadlock in rtnl_lock testing current HEAD 6dd0e32665e591e9debe3edaf73c2f8135bf047e testing commit 6dd0e32665e591e9debe3edaf73c2f8135bf047e with gcc (GCC) 8.1.0 kernel signature: 48b2f696e0142bab331f3547f6f6d2105bc84be6db7164f00eed29c898e57b9d all runs: crashed: possible deadlock in rtnl_lock revisions tested: 2, total time: 25m53.201190374s (build: 18m25.947725465s, test: 6m18.301989929s) the crash still happens on HEAD commit msg: Linux 4.19.115 crash: possible deadlock in rtnl_lock IPv6: ADDRCONF(NETDEV_CHANGE): vlan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vlan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready ============================================ WARNING: possible recursive locking detected 4.19.115-syzkaller #0 Not tainted -------------------------------------------- syz-executor.5/7655 is trying to acquire lock: 000000004ae598d0 (rtnl_mutex){+.+.}, at: rtnl_lock+0x12/0x20 net/core/rtnetlink.c:77 but task is already holding lock: 000000004ae598d0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline] 000000004ae598d0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x301/0x8f0 net/core/rtnetlink.c:4774 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(rtnl_mutex); lock(rtnl_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by syz-executor.5/7655: #0: 000000004ae598d0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline] #0: 000000004ae598d0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x301/0x8f0 net/core/rtnetlink.c:4774 stack backtrace: CPU: 0 PID: 7655 Comm: syz-executor.5 Not tainted 4.19.115-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x123/0x177 lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:1759 [inline] check_deadlock kernel/locking/lockdep.c:1803 [inline] validate_chain kernel/locking/lockdep.c:2399 [inline] __lock_acquire.cold.62+0x259/0x57a kernel/locking/lockdep.c:3411 lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3903 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf5/0x1210 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:77 hsr_dev_destroy+0x1a/0xb0 net/hsr/hsr_device.c:373 register_netdevice+0xa8a/0x1130 net/core/dev.c:8763 hsr_dev_finalize+0x4d2/0x720 net/hsr/hsr_device.c:491 hsr_newlink+0x228/0x330 net/hsr/hsr_netlink.c:72 rtnl_newlink+0xc78/0x1310 net/core/rtnetlink.c:3141 rtnetlink_rcv_msg+0x34f/0x8f0 net/core/rtnetlink.c:4777 netlink_rcv_skb+0x142/0x390 net/netlink/af_netlink.c:2455 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4795 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x443/0x650 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x765/0xc40 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xb5/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45af49 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fa2d881dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045af49 RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003 RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa2d881e6d4 R13: 00000000004ca811 R14: 00000000004e39b8 R15: 00000000ffffffff