====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc3-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor049/8419 is trying to acquire lock: ffff88814555f3a0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x24b/0xa00 block/genhd.c:610 but task is already holding lock: ffffffff8ca6fc08 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock lib/refcount.c:118 [inline] ffffffff8ca6fc08 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock+0x50/0x140 lib/refcount.c:113 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (nbd_index_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104 nbd_open+0x7d/0x8a0 drivers/block/nbd.c:1460 __blkdev_get+0x182/0xa30 fs/block_dev.c:1311 blkdev_get_by_dev fs/block_dev.c:1451 [inline] blkdev_get_by_dev+0x200/0x660 fs/block_dev.c:1423 blkdev_open+0x154/0x2b0 fs/block_dev.c:1546 do_dentry_open+0x4b9/0x11b0 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x1c0e/0x27e0 fs/namei.c:3494 do_filp_open+0x190/0x3d0 fs/namei.c:3521 do_sys_openat2+0x16d/0x420 fs/open.c:1187 do_sys_open fs/open.c:1203 [inline] __do_sys_open fs/open.c:1211 [inline] __se_sys_open fs/open.c:1207 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1207 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (&bdev->bd_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2938 [inline] check_prevs_add kernel/locking/lockdep.c:3061 [inline] validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902 lock_acquire kernel/locking/lockdep.c:5512 [inline] lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477 __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104 del_gendisk+0x24b/0xa00 block/genhd.c:610 nbd_dev_remove drivers/block/nbd.c:226 [inline] nbd_put.part.0+0xae/0x1e0 drivers/block/nbd.c:250 nbd_put drivers/block/nbd.c:1914 [inline] nbd_genl_connect+0x1214/0x1650 drivers/block/nbd.c:1968 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:800 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504 genl_rcv+0x24/0x40 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(nbd_index_mutex); lock(&bdev->bd_mutex); lock(nbd_index_mutex); lock(&bdev->bd_mutex); *** DEADLOCK *** 3 locks held by syz-executor049/8419: #0: ffffffff8d736410 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:810 #1: ffffffff8d7364c8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline] #1: ffffffff8d7364c8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x3e0/0x580 net/netlink/genetlink.c:798 #2: ffffffff8ca6fc08 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock lib/refcount.c:118 [inline] #2: ffffffff8ca6fc08 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock+0x50/0x140 lib/refcount.c:113 stack backtrace: CPU: 0 PID: 8419 Comm: syz-executor049 Not tainted 5.13.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x141/0x1d7 lib/dump_stack.c:120 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2129 check_prev_add kernel/locking/lockdep.c:2938 [inline] check_prevs_add kernel/locking/lockdep.c:3061 [inline] validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902 lock_acquire kernel/locking/lockdep.c:5512 [inline] lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477 __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104 del_gendisk+0x24b/0xa00 block/genhd.c:610 nbd_dev_remove drivers/block/nbd.c:226 [inline] nbd_put.part.0+0xae/0x1e0 drivers/block/nbd.c:250 nbd_put drivers/block/nbd.c:1914 [inline] nbd_genl_connect+0x1214/0x1650 drivers/block/nbd.c:1968 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:800 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504 genl_rcv+0x24/0x40 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x43fa59 Code: 28 c3 e8 5a 14 00 00 66 2e 0f 1f 84 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffce87347a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004004a0 RCX: 000000000043fa59 RDX: 0000000000000000 RSI: 0000000020000d00 RDI: 0000000000000003 RBP: 00000000004034c0 R08: 0000000000000002 R09: 00000000004004a0 R10: 000000000000000c R11: 0000000000000246 R12: 0000000000403550 R13: 0000000000000000 R14: 00000000004ad018 R15: 00000000004004a0