bisecting fixing commit since 3d40d7117e353b84627c1e8c5ed9ae0b1237ef5c building syzkaller on 438e1227121e9d4bbca7b12b6e1b715524d512c2 testing commit 3d40d7117e353b84627c1e8c5ed9ae0b1237ef5c with gcc (GCC) 8.1.0 kernel signature: 7e808949aae6f48ad64c6bf4d492de685fbe6bf07dd64ac177b58172fd2283ab all runs: crashed: possible deadlock in rtnl_lock testing current HEAD 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e testing commit 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e with gcc (GCC) 8.1.0 kernel signature: 6ca570350ef583d7f194ff5f9d6543062cb2834d7beed80dc7a5e4b89140c970 all runs: crashed: possible deadlock in rtnl_lock revisions tested: 2, total time: 27m50.154390068s (build: 19m58.348500931s, test: 5m59.344789874s) the crash still happens on HEAD commit msg: Linux 4.19.123 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 4.19.123-syzkaller #0 Not tainted -------------------------------------------- syz-executor.0/7676 is trying to acquire lock: 000000008311dcd0 (rtnl_mutex){+.+.}, at: rtnl_lock+0x12/0x20 net/core/rtnetlink.c:77 but task is already holding lock: 000000008311dcd0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline] 000000008311dcd0 (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.0/7676: #0: 000000008311dcd0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline] #0: 000000008311dcd0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x301/0x8f0 net/core/rtnetlink.c:4774 stack backtrace: CPU: 0 PID: 7676 Comm: syz-executor.0 Not tainted 4.19.123-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:1763 [inline] check_deadlock kernel/locking/lockdep.c:1807 [inline] validate_chain kernel/locking/lockdep.c:2403 [inline] __lock_acquire.cold.62+0x259/0x57a kernel/locking/lockdep.c:3415 lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3907 __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:8764 hsr_dev_finalize+0x4d2/0x720 net/hsr/hsr_device.c:491 hsr_newlink+0x22f/0x3c0 net/hsr/hsr_netlink.c:78 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:00007f344e3bcc78 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: 00007f344e3bd6d4 R13: 00000000004ca811 R14: 00000000004e39b8 R15: 00000000ffffffff