syzbot

ubi31: attaching mtd0
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.2.3151/14986 is trying to acquire lock:
ffffffff8deee4a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8deee4a0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline]
ffffffff8deee4a0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline]
ffffffff8deee4a0 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_noprof+0x44/0x680 mm/slub.c:4873

but task is already holding lock:
ffffffff8ded27e0 (slab_mutex){+.+.}-{4:4}, at: __kmem_cache_create_args+0x58/0x450 mm/slab_common.c:350

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (slab_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       kmem_cache_destroy+0x64/0x170 mm/slab_common.c:557
       p9_client_destroy+0x4c2/0x510 net/9p/client.c:965
       v9fs_session_close+0x4f/0x200 fs/9p/v9fs.c:539
       v9fs_kill_super+0x5c/0x90 fs/9p/vfs_super.c:175
       deactivate_locked_super+0xbc/0x130 fs/super.c:476
       v9fs_get_tree+0x846/0xac0 fs/9p/vfs_super.c:156
       vfs_get_tree+0x92/0x2a0 fs/super.c:1754
       fc_mount fs/namespace.c:1193 [inline]
       do_new_mount_fc fs/namespace.c:3763 [inline]
       do_new_mount+0x341/0xd30 fs/namespace.c:3839
       do_mount fs/namespace.c:4172 [inline]
       __do_sys_mount fs/namespace.c:4361 [inline]
       __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:490
       static_key_disable+0x12/0x20 kernel/jump_label.c:247
       __inet_hash_connect+0x2486/0x2490 net/ipv4/inet_hashtables.c:1074
       tcp_v4_connect+0xd5f/0x19b0 net/ipv4/tcp_ipv4.c:307
       __inet_stream_connect+0x25a/0xdd0 net/ipv4/af_inet.c:685
       inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:756
       __sys_connect_file net/socket.c:2089 [inline]
       __sys_connect+0x315/0x450 net/socket.c:2108
       __do_sys_connect net/socket.c:2114 [inline]
       __se_sys_connect net/socket.c:2111 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2111
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x3e/0x130 net/core/sock.c:3780
       lock_sock include/net/sock.h:1709 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:919
       nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
       sock_shutdown+0x15e/0x260 drivers/block/nbd.c:411
       nbd_clear_sock+0x24/0x170 drivers/block/nbd.c:1427
       nbd_clear_sock_ioctl drivers/block/nbd.c:1575 [inline]
       __nbd_ioctl drivers/block/nbd.c:1603 [inline]
       nbd_ioctl+0x337/0xe40 drivers/block/nbd.c:1663
       blkdev_ioctl+0x5e6/0x750 block/ioctl.c:804
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0xa77/0x1910 block/blk-mq.c:2148
       __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+0xddb/0x1610 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xda/0x1a0 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x368/0x520 block/blk-mq.c:2386
       blk_mq_dispatch_list+0xd1f/0xe20 include/linux/spinlock_rt.h:-1
       blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x28d/0x580 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x599/0x830 fs/buffer.c:2444
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x2bf/0x560 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb8/0x2b0 block/partitions/core.c:723
       adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694
       blkdev_get_whole+0x2e5/0x480 block/bdev.c:764
       bdev_open+0x31e/0xcc0 block/bdev.c:973
       blkdev_open+0x485/0x620 block/fops.c:697
       do_dentry_open+0x83d/0x13e0 fs/open.c:949
       vfs_open+0x3b/0x350 fs/open.c:1081
       do_open fs/namei.c:4677 [inline]
       path_openat+0x2e43/0x38a0 fs/namei.c:4836
       do_file_open+0x23e/0x4a0 fs/namei.c:4865
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0xa77/0x1910 block/blk-mq.c:2148
       __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+0xddb/0x1610 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xda/0x1a0 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x368/0x520 block/blk-mq.c:2386
       blk_mq_dispatch_list+0xd1f/0xe20 include/linux/spinlock_rt.h:-1
       blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x28d/0x580 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x599/0x830 fs/buffer.c:2444
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x2bf/0x560 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb8/0x2b0 block/partitions/core.c:723
       adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694
       blkdev_get_whole+0x2e5/0x480 block/bdev.c:764
       bdev_open+0x31e/0xcc0 block/bdev.c:973
       blkdev_open+0x485/0x620 block/fops.c:697
       do_dentry_open+0x83d/0x13e0 fs/open.c:949
       vfs_open+0x3b/0x350 fs/open.c:1081
       do_open fs/namei.c:4677 [inline]
       path_openat+0x2e43/0x38a0 fs/namei.c:4836
       do_file_open+0x23e/0x4a0 fs/namei.c:4865
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:199 [inline]
       __synchronize_srcu+0xca/0x300 kernel/rcu/srcutree.c:1481
       elevator_switch+0x1e8/0x7a0 block/elevator.c:576
       elevator_change+0x2cc/0x450 block/elevator.c:681
       elevator_set_default+0x36c/0x430 block/elevator.c:754
       blk_register_queue+0x366/0x430 block/blk-sysfs.c:946
       __add_disk+0x677/0xd50 block/genhd.c:528
       add_disk_fwnode+0xfb/0x480 block/genhd.c:597
       add_disk include/linux/blkdev.h:785 [inline]
       nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x8d0 init/main.c:1382
       do_initcall_level+0x104/0x190 init/main.c:1444
       do_initcalls+0x59/0xa0 init/main.c:1460
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
       kernel_init+0x1d/0x1d0 init/main.c:1582
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       elevator_change+0x1b3/0x450 block/elevator.c:679
       elevator_set_none+0xb5/0x140 block/elevator.c:769
       blk_mq_elv_switch_none block/blk-mq.c:5110 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5155 [inline]
       blk_mq_update_nr_hw_queues+0x607/0x1a80 block/blk-mq.c:5220
       nbd_start_device+0x17f/0xb20 drivers/block/nbd.c:1489
       nbd_genl_connect+0x1651/0x1c80 drivers/block/nbd.c:2239
       genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x831/0x9f0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg net/socket.c:742 [inline]
       ____sys_sendmsg+0x94c/0x9c0 net/socket.c:2592
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x1c3/0x2a0 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       blk_alloc_queue+0x54e/0x690 block/blk-core.c:461
       blk_mq_alloc_queue block/blk-mq.c:4429 [inline]
       __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4476
       nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x8d0 init/main.c:1382
       do_initcall_level+0x104/0x190 init/main.c:1444
       do_initcalls+0x59/0xa0 init/main.c:1460
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
       kernel_init+0x1d/0x1d0 init/main.c:1582
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
       __fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4362
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4489 [inline]
       slab_alloc_node mm/slub.c:4843 [inline]
       kmem_cache_alloc_noprof+0x44/0x680 mm/slub.c:4873
       create_cache mm/slab_common.c:249 [inline]
       __kmem_cache_create_args+0x301/0x450 mm/slab_common.c:380
       __kmem_cache_create include/linux/slab.h:390 [inline]
       alloc_ai drivers/mtd/ubi/attach.c:1464 [inline]
       ubi_attach+0x2c9/0x5030 drivers/mtd/ubi/attach.c:1560
       ubi_attach_mtd_dev+0x1ab7/0x38e0 drivers/mtd/ubi/build.c:1004
       ctrl_cdev_ioctl+0x2fc/0x480 drivers/mtd/ubi/cdev.c:1113
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 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:
  fs_reclaim --> cpu_hotplug_lock --> slab_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(slab_mutex);
                               lock(cpu_hotplug_lock);
                               lock(slab_mutex);
  lock(fs_reclaim);

 *** DEADLOCK ***

2 locks held by syz.2.3151/14986:
 #0: ffffffff8e864598 (ubi_devices_mutex){+.+.}-{4:4}, at: ctrl_cdev_ioctl+0x298/0x480 drivers/mtd/ubi/cdev.c:1112
 #1: ffffffff8ded27e0 (slab_mutex){+.+.}-{4:4}, at: __kmem_cache_create_args+0x58/0x450 mm/slab_common.c:350

stack backtrace:
CPU: 0 UID: 0 PID: 14986 Comm: syz.2.3151 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 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 kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 __fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
 fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4362
 might_alloc include/linux/sched/mm.h:317 [inline]
 slab_pre_alloc_hook mm/slub.c:4489 [inline]
 slab_alloc_node mm/slub.c:4843 [inline]
 kmem_cache_alloc_noprof+0x44/0x680 mm/slub.c:4873
 create_cache mm/slab_common.c:249 [inline]
 __kmem_cache_create_args+0x301/0x450 mm/slab_common.c:380
 __kmem_cache_create include/linux/slab.h:390 [inline]
 alloc_ai drivers/mtd/ubi/attach.c:1464 [inline]
 ubi_attach+0x2c9/0x5030 drivers/mtd/ubi/attach.c:1560
 ubi_attach_mtd_dev+0x1ab7/0x38e0 drivers/mtd/ubi/build.c:1004
 ctrl_cdev_ioctl+0x2fc/0x480 drivers/mtd/ubi/cdev.c:1113
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd0708dc819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd06eb0d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd070b56090 RCX: 00007fd0708dc819
RDX: 0000200000000440 RSI: 0000000040186f40 RDI: 0000000000000003
RBP: 00007fd070972c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd070b56128 R14: 00007fd070b56090 R15: 00007fff61f5bff8
 </TASK>
ubi31: scanning is finished
ubi31: empty MTD device detected
ubi31: attached mtd0 (name "mtdram test device", size 0 MiB)
ubi31: PEB size: 4096 bytes (4 KiB), LEB size: 3968 bytes
ubi31: min./max. I/O unit sizes: 1/64, sub-page size 1
ubi31: VID header offset: 64 (aligned 64), data offset: 128
ubi31: good PEBs: 32, bad PEBs: 0, corrupted PEBs: 0
ubi31: user volume: 0, internal volumes: 1, max. volumes count: 23
ubi31: max/mean erase counter: 0/0, WL threshold: 4096, image sequence number: 1002982318
ubi31: available PEBs: 28, total reserved PEBs: 4, PEBs reserved for bad PEB handling: 0