possible deadlock in do_tcp_setsockopt

Status: fixed on 2025/10/29 21:02
Subsystems: net
[Documentation on labels]
Fix commit: 9f7c02e03157 nbd: restrict sockets to TCP and UDP
First crash: 343d, last: 343d
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 possible deadlock in do_tcp_setsockopt 4 47 1892d 2351d 0/1 auto-closed as invalid on 2021/10/08 10:18

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.9212/1116 is trying to acquire lock:
ffff88805ee281e0 (&mm->mmap_lock){++++}-{4:4}, at: __might_fault+0xb0/0x130 mm/memory.c:7086

but task is already holding lock:
ffff888046a6a8a0 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: do_tcp_setsockopt+0x854/0x1f20 net/ipv4/tcp.c:3897

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (k-sk_lock-AF_INET){+.+.}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       lock_sock_fast include/net/sock.h:1708 [inline]
       mptcp_setsockopt_sol_socket_tstamp net/mptcp/sockopt.c:162 [inline]
       mptcp_setsockopt_sol_socket_int net/mptcp/sockopt.c:199 [inline]
       mptcp_setsockopt_sol_socket net/mptcp/sockopt.c:335 [inline]
       mptcp_setsockopt+0x2117/0x3560 net/mptcp/sockopt.c:901
       do_sock_setsockopt+0x179/0x1b0 net/socket.c:2344
       __sys_setsockopt net/socket.c:2369 [inline]
       __do_sys_setsockopt net/socket.c:2375 [inline]
       __se_sys_setsockopt net/socket.c:2372 [inline]
       __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2372
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       lock_sock_nested+0x48/0x100 net/core/sock.c:3716
       lock_sock include/net/sock.h:1676 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:905
       nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
       sock_shutdown+0x15e/0x260 drivers/block/nbd.c:411
       nbd_clear_sock drivers/block/nbd.c:1416 [inline]
       nbd_config_put+0x342/0x790 drivers/block/nbd.c:1440
       nbd_release+0xfe/0x140 drivers/block/nbd.c:1745
       bdev_release+0x536/0x650 block/bdev.c:-1
       blkdev_release+0x15/0x20 block/fops.c:702
       __fput+0x449/0xa70 fs/file_table.c:468
       task_work_run+0x1d1/0x260 kernel/task_work.c:227
       exit_task_work include/linux/task_work.h:40 [inline]
       do_exit+0x6b5/0x2300 kernel/exit.c:966
       do_group_exit+0x21c/0x2d0 kernel/exit.c:1107
       get_signal+0x1286/0x1340 kernel/signal.c:3034
       arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337
       exit_to_user_mode_loop+0x75/0x130 kernel/entry/common.c:40
       exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
       syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
       syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
       do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       nbd_handle_cmd drivers/block/nbd.c:1140 [inline]
       nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204
       blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2120
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2358
       blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2967
       __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220
       blk_finish_plug block/blk-core.c:1247 [inline]
       __submit_bio+0x2d3/0x5a0 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751
       submit_bh fs/buffer.c:2829 [inline]
       block_read_full_folio+0x599/0x830 fs/buffer.c:2447
       filemap_read_folio+0x114/0x380 mm/filemap.c:2426
       do_read_cache_folio+0x350/0x590 mm/filemap.c:3983
       read_mapping_folio include/linux/pagemap.h:999 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
       adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:141 [inline]
       blk_add_partitions block/partitions/core.c:589 [inline]
       bdev_disk_changed+0x75c/0x14b0 block/partitions/core.c:693
       blkdev_get_whole+0x380/0x510 block/bdev.c:748
       bdev_open+0x31e/0xd30 block/bdev.c:957
       blkdev_open+0x457/0x600 block/fops.c:694
       do_dentry_open+0x950/0x13f0 fs/open.c:965
       vfs_open+0x3b/0x340 fs/open.c:1095
       do_open fs/namei.c:3887 [inline]
       path_openat+0x2ee5/0x3830 fs/namei.c:4046
       do_filp_open+0x1fa/0x410 fs/namei.c:4073
       do_sys_openat2+0x121/0x1c0 fs/open.c:1435
       do_sys_open fs/open.c:1450 [inline]
       __do_sys_openat fs/open.c:1466 [inline]
       __se_sys_openat fs/open.c:1461 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1461
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&cmd->lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196
       blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2120
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2358
       blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2967
       __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220
       blk_finish_plug block/blk-core.c:1247 [inline]
       __submit_bio+0x2d3/0x5a0 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751
       submit_bh fs/buffer.c:2829 [inline]
       __bread_slow fs/buffer.c:1272 [inline]
       __bread_gfp+0x216/0x3c0 fs/buffer.c:1518
       sb_bread include/linux/buffer_head.h:346 [inline]
       fat_fill_super+0x5e2/0x3570 fs/fat/inode.c:1600
       get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1691
       vfs_get_tree+0x8f/0x2b0 fs/super.c:1751
       fc_mount fs/namespace.c:1274 [inline]
       do_new_mount_fc fs/namespace.c:3726 [inline]
       do_new_mount+0x302/0xa10 fs/namespace.c:3802
       do_mount fs/namespace.c:4125 [inline]
       __do_sys_mount fs/namespace.c:4324 [inline]
       __se_sys_mount+0x313/0x410 fs/namespace.c:4301
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (set->srcu){.+.+}-{0:0}:
       lock_sync+0xba/0x160 kernel/locking/lockdep.c:5916
       srcu_lock_sync include/linux/srcu.h:173 [inline]
       __synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1429
       elevator_switch+0x12b/0x640 block/elevator.c:588
       elevator_change+0x2d4/0x450 block/elevator.c:690
       elevator_set_default+0x186/0x260 block/elevator.c:766
       blk_register_queue+0x34e/0x3f0 block/blk-sysfs.c:904
       __add_disk+0x677/0xd50 block/genhd.c:528
       add_disk_fwnode+0xfc/0x480 block/genhd.c:597
       add_disk include/linux/blkdev.h:774 [inline]
       nbd_dev_add+0x717/0xae0 drivers/block/nbd.c:1973
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2680
       do_one_initcall+0x233/0x820 init/main.c:1281
       do_initcall_level+0x104/0x190 init/main.c:1343
       do_initcalls+0x59/0xa0 init/main.c:1359
       kernel_init_freeable+0x334/0x4b0 init/main.c:1591
       kernel_init+0x1d/0x1d0 init/main.c:1481
       ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       elevator_change+0x19b/0x450 block/elevator.c:688
       elevator_set_none+0x42/0xb0 block/elevator.c:781
       blk_mq_elv_switch_none block/blk-mq.c:5023 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5066 [inline]
       blk_mq_update_nr_hw_queues+0x598/0x1aa0 block/blk-mq.c:5124
       nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1478
       nbd_genl_connect+0x135b/0x18f0 drivers/block/nbd.c:2228
       genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115
       genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
       genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x82c/0x9e0 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
       sock_sendmsg_nosec net/socket.c:714 [inline]
       __sock_sendmsg+0x219/0x270 net/socket.c:729
       ____sys_sendmsg+0x505/0x830 net/socket.c:2614
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668
       __sys_sendmsg net/socket.c:2700 [inline]
       __do_sys_sendmsg net/socket.c:2705 [inline]
       __se_sys_sendmsg net/socket.c:2703 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2703
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       blk_alloc_queue+0x538/0x620 block/blk-core.c:461
       blk_mq_alloc_queue block/blk-mq.c:4400 [inline]
       __blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4447
       nbd_dev_add+0x46c/0xae0 drivers/block/nbd.c:1943
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2680
       do_one_initcall+0x233/0x820 init/main.c:1281
       do_initcall_level+0x104/0x190 init/main.c:1343
       do_initcalls+0x59/0xa0 init/main.c:1359
       kernel_init_freeable+0x334/0x4b0 init/main.c:1591
       kernel_init+0x1d/0x1d0 init/main.c:1481
       ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __fs_reclaim_acquire mm/page_alloc.c:4239 [inline]
       fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4253
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4661 [inline]
       slab_alloc_node mm/slub.c:4984 [inline]
       kmem_cache_alloc_noprof+0x45/0x6e0 mm/slub.c:5015
       mt_alloc_one lib/maple_tree.c:176 [inline]
       mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1130
       mas_preallocate+0x2c5/0x550 lib/maple_tree.c:5374
       vma_iter_prealloc mm/vma.h:462 [inline]
       vma_link+0xfd/0x440 mm/vma.c:1792
       insert_vm_struct+0x199/0x260 mm/vma.c:3196
       create_init_stack_vma+0x2de/0x680 mm/vma_exec.c:143
       bprm_mm_init fs/exec.c:274 [inline]
       alloc_bprm+0x496/0x5c0 fs/exec.c:1466
       kernel_execve+0x9b/0x9f0 fs/exec.c:1885
       try_to_run_init_process+0x13/0x60 init/main.c:1409
       kernel_init+0xad/0x1d0 init/main.c:1537
       ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (&mm->mmap_lock){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __might_fault+0xcc/0x130 mm/memory.c:7086
       _inline_copy_from_user include/linux/uaccess.h:162 [inline]
       _copy_from_user+0x28/0xb0 lib/usercopy.c:18
       copy_from_user include/linux/uaccess.h:212 [inline]
       copy_from_sockptr_offset include/linux/sockptr.h:48 [inline]
       copy_from_sockptr include/linux/sockptr.h:61 [inline]
       tcp_v4_parse_md5_keys+0xec/0x600 net/ipv4/tcp_ipv4.c:1526
       do_tcp_setsockopt+0x11dc/0x1f20 net/ipv4/tcp.c:4028
       smc_setsockopt+0x22f/0xab0 net/smc/af_smc.c:3100
       do_sock_setsockopt+0x179/0x1b0 net/socket.c:2344
       __sys_setsockopt net/socket.c:2369 [inline]
       __do_sys_setsockopt net/socket.c:2375 [inline]
       __se_sys_setsockopt net/socket.c:2372 [inline]
       __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2372
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &mm->mmap_lock --> sk_lock-AF_INET --> k-sk_lock-AF_INET

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(k-sk_lock-AF_INET);
                               lock(sk_lock-AF_INET);
                               lock(k-sk_lock-AF_INET);
  rlock(&mm->mmap_lock);

 *** DEADLOCK ***

2 locks held by syz.6.9212/1116:
 #0: ffff88806896d510 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_setsockopt+0x181/0xab0 net/smc/af_smc.c:3092
 #1: ffff888046a6a8a0 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: do_tcp_setsockopt+0x854/0x1f20 net/ipv4/tcp.c:3897

stack backtrace:
CPU: 1 UID: 0 PID: 1116 Comm: syz.6.9212 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __might_fault+0xcc/0x130 mm/memory.c:7086
 _inline_copy_from_user include/linux/uaccess.h:162 [inline]
 _copy_from_user+0x28/0xb0 lib/usercopy.c:18
 copy_from_user include/linux/uaccess.h:212 [inline]
 copy_from_sockptr_offset include/linux/sockptr.h:48 [inline]
 copy_from_sockptr include/linux/sockptr.h:61 [inline]
 tcp_v4_parse_md5_keys+0xec/0x600 net/ipv4/tcp_ipv4.c:1526
 do_tcp_setsockopt+0x11dc/0x1f20 net/ipv4/tcp.c:4028
 smc_setsockopt+0x22f/0xab0 net/smc/af_smc.c:3100
 do_sock_setsockopt+0x179/0x1b0 net/socket.c:2344
 __sys_setsockopt net/socket.c:2369 [inline]
 __do_sys_setsockopt net/socket.c:2375 [inline]
 __se_sys_setsockopt net/socket.c:2372 [inline]
 __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2372
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f942af8ebe9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f942be24038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f942b1c5fa0 RCX: 00007f942af8ebe9
RDX: 0000000000000020 RSI: 0000000000000006 RDI: 0000000000000003
RBP: 00007f942b011e19 R08: 00000000000000d8 R09: 0000000000000000
R10: 0000200000000180 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f942b1c6038 R14: 00007f942b1c5fa0 R15: 00007ffe771bf3b8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/05 13:15 linux-next be5d4872e528 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in do_tcp_setsockopt
* Struck through repros no longer work on HEAD.