============================================ WARNING: possible recursive locking detected 4.15.0-rc2-mm1+ #39 Not tainted -------------------------------------------- syz-executor1/16190 is trying to acquire lock: (rtnl_mutex){+.+.}, at: [<00000000027f6754>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 but task is already holding lock: (rtnl_mutex){+.+.}, at: [<00000000027f6754>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 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-executor1/16190: #0: (rtnl_mutex){+.+.}, at: [<00000000027f6754>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 stack backtrace: CPU: 0 PID: 16190 Comm: syz-executor1 Not tainted 4.15.0-rc2-mm1+ #39 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_deadlock_bug kernel/locking/lockdep.c:1809 [inline] check_deadlock kernel/locking/lockdep.c:1856 [inline] validate_chain kernel/locking/lockdep.c:2457 [inline] __lock_acquire+0x11cf/0x47f0 kernel/locking/lockdep.c:3500 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 tun_free_netdev+0x158/0x1f0 drivers/net/tun.c:2068 register_netdevice+0x97b/0x1010 net/core/dev.c:7774 tun_set_iff drivers/net/tun.c:2389 [inline] __tun_chr_ioctl+0x1ca3/0x3f10 drivers/net/tun.c:2613 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2866 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x452a09 RSP: 002b:00007f0a4d0b4c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0a4d0b5700 RCX: 0000000000452a09 RDX: 0000000020f58000 RSI: 00000000400454ca RDI: 0000000000000013 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000 R13: 0000000000a2f7ff R14: 00007f0a4d0b59c0 R15: 0000000000000000