====================================================== WARNING: possible circular locking dependency detected 5.12.0-rc4-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/10107 is trying to acquire lock: ffff88801767dca0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x225/0x960 block/genhd.c:684 but task is already holding lock: ffffffff8af82810 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x1f7/0x960 block/genhd.c:682 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (bdev_lookup_sem){++++}-{3:3}: down_write+0x92/0x150 kernel/locking/rwsem.c:1406 del_gendisk+0x1f7/0x960 block/genhd.c:682 nbd_dev_remove drivers/block/nbd.c:226 [inline] nbd_put.part.0+0xa4/0x1b0 drivers/block/nbd.c:250 nbd_put drivers/block/nbd.c:1928 [inline] nbd_genl_connect+0xeee/0x1290 drivers/block/nbd.c:1968 genl_family_rcv_msg_doit+0x1e4/0x2f0 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x27a/0x4a0 net/netlink/genetlink.c:800 netlink_rcv_skb+0x118/0x370 net/netlink/af_netlink.c:2502 genl_rcv+0x1f/0x30 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x42e/0x700 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x70e/0xbe0 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xab/0xe0 net/socket.c:674 ____sys_sendmsg+0x5bf/0x7a0 net/socket.c:2350 ___sys_sendmsg+0xd3/0x150 net/socket.c:2404 __sys_sendmsg+0xb2/0x140 net/socket.c:2433 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (nbd_index_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 nbd_open+0x6f/0x630 drivers/block/nbd.c:1460 __blkdev_get+0x10a/0x8d0 fs/block_dev.c:1304 blkdev_get_by_dev fs/block_dev.c:1456 [inline] blkdev_get_by_dev+0x1fb/0x510 fs/block_dev.c:1424 blkdev_open+0xf6/0x220 fs/block_dev.c:1553 do_dentry_open+0x42a/0xfb0 fs/open.c:826 do_open fs/namei.c:3365 [inline] path_openat+0x9ee/0x22b0 fs/namei.c:3498 do_filp_open+0x16d/0x390 fs/namei.c:3525 do_sys_openat2+0x11e/0x360 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+0xfd/0x1a0 fs/open.c:1207 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (&bdev->bd_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2936 [inline] check_prevs_add kernel/locking/lockdep.c:3059 [inline] validate_chain kernel/locking/lockdep.c:3674 [inline] __lock_acquire+0x2b37/0x57d0 kernel/locking/lockdep.c:4900 lock_acquire kernel/locking/lockdep.c:5510 [inline] lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475 __mutex_lock_common kernel/locking/mutex.c:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 del_gendisk+0x225/0x960 block/genhd.c:684 nbd_dev_remove drivers/block/nbd.c:226 [inline] nbd_put.part.0+0xa4/0x1b0 drivers/block/nbd.c:250 nbd_put drivers/block/nbd.c:1928 [inline] nbd_genl_connect+0xeee/0x1290 drivers/block/nbd.c:1968 genl_family_rcv_msg_doit+0x1e4/0x2f0 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x27a/0x4a0 net/netlink/genetlink.c:800 netlink_rcv_skb+0x118/0x370 net/netlink/af_netlink.c:2502 genl_rcv+0x1f/0x30 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x42e/0x700 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x70e/0xbe0 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xab/0xe0 net/socket.c:674 ____sys_sendmsg+0x5bf/0x7a0 net/socket.c:2350 ___sys_sendmsg+0xd3/0x150 net/socket.c:2404 __sys_sendmsg+0xb2/0x140 net/socket.c:2433 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: &bdev->bd_mutex --> nbd_index_mutex --> bdev_lookup_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(bdev_lookup_sem); lock(nbd_index_mutex); lock(bdev_lookup_sem); lock(&bdev->bd_mutex); *** DEADLOCK *** 4 locks held by syz-executor.2/10107: #0: ffffffff8be306b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x10/0x30 net/netlink/genetlink.c:810 #1: ffffffff8be30768 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline] #1: ffffffff8be30768 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x315/0x4a0 net/netlink/genetlink.c:798 #2: ffffffff8b1f7b68 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock lib/refcount.c:118 [inline] #2: ffffffff8b1f7b68 (nbd_index_mutex){+.+.}-{3:3}, at: refcount_dec_and_mutex_lock+0x2b/0xd0 lib/refcount.c:113 #3: ffffffff8af82810 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x1f7/0x960 block/genhd.c:682 stack backtrace: CPU: 0 PID: 10107 Comm: syz-executor.2 Not tainted 5.12.0-rc4-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+0xa5/0xe6 lib/dump_stack.c:120 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2127 check_prev_add kernel/locking/lockdep.c:2936 [inline] check_prevs_add kernel/locking/lockdep.c:3059 [inline] validate_chain kernel/locking/lockdep.c:3674 [inline] __lock_acquire+0x2b37/0x57d0 kernel/locking/lockdep.c:4900 lock_acquire kernel/locking/lockdep.c:5510 [inline] lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475 __mutex_lock_common kernel/locking/mutex.c:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 del_gendisk+0x225/0x960 block/genhd.c:684 nbd_dev_remove drivers/block/nbd.c:226 [inline] nbd_put.part.0+0xa4/0x1b0 drivers/block/nbd.c:250 nbd_put drivers/block/nbd.c:1928 [inline] nbd_genl_connect+0xeee/0x1290 drivers/block/nbd.c:1968 genl_family_rcv_msg_doit+0x1e4/0x2f0 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x27a/0x4a0 net/netlink/genetlink.c:800 netlink_rcv_skb+0x118/0x370 net/netlink/af_netlink.c:2502 genl_rcv+0x1f/0x30 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x42e/0x700 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x70e/0xbe0 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xab/0xe0 net/socket.c:674 ____sys_sendmsg+0x5bf/0x7a0 net/socket.c:2350 ___sys_sendmsg+0xd3/0x150 net/socket.c:2404 __sys_sendmsg+0xb2/0x140 net/socket.c:2433 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4665d9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f8cc0dbb188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9 RDX: 0000000000000800 RSI: 0000000020000340 RDI: 0000000000000005 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007ffe4a5f58ff R14: 00007f8cc0dbb300 R15: 0000000000022000