======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.16/6352 is trying to acquire lock:
ffff888071442280 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff888071442280 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: lookup_slow+0x42/0x70 fs/namei.c:1935

but task is already holding lock:
ffffffff8ec9c4c0 (param_lock){+.+.}-{4:4}, at: kernel_param_lock kernel/params.c:604 [inline]
ffffffff8ec9c4c0 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xec/0x300 kernel/params.c:589

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (param_lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       ieee80211_rate_control_ops_get net/mac80211/rate.c:221 [inline]
       rate_control_alloc net/mac80211/rate.c:267 [inline]
       ieee80211_init_rate_ctrl_alg+0x1df/0x3b0 net/mac80211/rate.c:1016
       ieee80211_register_hw+0x2c5b/0x45c0 net/mac80211/main.c:1565
       mac80211_hwsim_new_radio+0x2b08/0x6510 drivers/net/wireless/virtual/mac80211_hwsim_main.c:6143
       init_mac80211_hwsim+0x5e2/0x6f0 drivers/net/wireless/virtual/mac80211_hwsim_main.c:7633
       do_one_initcall+0x11c/0x6f0 init/main.c:1362
       do_initcall_level init/main.c:1424 [inline]
       do_initcalls init/main.c:1440 [inline]
       do_basic_setup init/main.c:1460 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1675
       kernel_init+0x21/0x1e0 init/main.c:1565
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (rtnl_mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       cgrp_css_online+0xa1/0x1f0 net/core/netprio_cgroup.c:157
       online_css+0xb2/0x350 kernel/cgroup/cgroup.c:5871
       css_create kernel/cgroup/cgroup.c:5949 [inline]
       cgroup_apply_control_enable+0xa8d/0xdd0 kernel/cgroup/cgroup.c:3460
       cgroup_mkdir+0x57f/0x1330 kernel/cgroup/cgroup.c:6150
       kernfs_iop_mkdir+0x111/0x190 fs/kernfs/dir.c:1305
       vfs_mkdir+0x364/0x850 fs/namei.c:5410
       filename_mkdirat+0x48b/0x5e0 fs/namei.c:5443
       __do_sys_mkdirat fs/namei.c:5464 [inline]
       __se_sys_mkdirat fs/namei.c:5461 [inline]
       __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5461
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (cgroup_mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       cgroup_lock include/linux/cgroup.h:482 [inline]
       cgroup_kn_lock_live+0x116/0x520 kernel/cgroup/cgroup.c:1719
       cgroup_rmdir+0x22/0x2f0 kernel/cgroup/cgroup.c:6402
       kernfs_iop_rmdir+0x106/0x170 fs/kernfs/dir.c:1323
       vfs_rmdir fs/namei.c:5515 [inline]
       vfs_rmdir+0x328/0x8a0 fs/namei.c:5488
       filename_rmdir+0x31a/0x5c0 fs/namei.c:5572
       __do_sys_rmdir fs/namei.c:5595 [inline]
       __se_sys_rmdir fs/namei.c:5592 [inline]
       __x64_sys_rmdir+0x46/0x70 fs/namei.c:5592
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&type->i_mutex_dir_key#6){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       inode_lock_shared include/linux/fs.h:1039 [inline]
       lookup_slow+0x42/0x70 fs/namei.c:1935
       walk_component fs/namei.c:2282 [inline]
       lookup_last fs/namei.c:2789 [inline]
       path_lookupat+0x5e8/0xc40 fs/namei.c:2813
       filename_lookup+0x202/0x590 fs/namei.c:2842
       kern_path+0x37/0x50 fs/namei.c:3036
       lookup_bdev+0xd8/0x2a0 block/bdev.c:1268
       bdev_file_open_by_path+0x82/0x330 block/bdev.c:1123
       add_device drivers/mtd/devices/block2mtd.c:279 [inline]
       block2mtd_setup2.isra.0+0x2ee/0xbd0 drivers/mtd/devices/block2mtd.c:459
       block2mtd_setup+0xbd/0xd0 drivers/mtd/devices/block2mtd.c:476
       param_attr_store+0x199/0x300 kernel/params.c:591
       module_attr_store+0x58/0x80 kernel/params.c:906
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6af/0x1050 fs/read_write.c:687
       ksys_write+0x12a/0x250 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &type->i_mutex_dir_key#6 --> rtnl_mutex --> param_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(param_lock);
                               lock(rtnl_mutex);
                               lock(param_lock);
  rlock(&type->i_mutex_dir_key#6);

 *** DEADLOCK ***

locks held by syz.0.16/6352: 5, last CPU#0:
 #0: ffff88807fa637b0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888035b28460 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffff88807f8f7480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:336
 #3: ffff88803574bb48 (kn->active#4){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
 #3: ffff88803574bb48 (kn->active#4){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x332/0x5f0 fs/kernfs/file.c:337
 #4: ffffffff8ec9c4c0 (param_lock){+.+.}-{4:4}, at: kernel_param_lock kernel/params.c:604 [inline]
 #4: ffffffff8ec9c4c0 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xec/0x300 kernel/params.c:589

stack backtrace:
CPU: 0 UID: 0 PID: 6352 Comm: syz.0.16 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 inode_lock_shared include/linux/fs.h:1039 [inline]
 lookup_slow+0x42/0x70 fs/namei.c:1935
 walk_component fs/namei.c:2282 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x5e8/0xc40 fs/namei.c:2813
 filename_lookup+0x202/0x590 fs/namei.c:2842
 kern_path+0x37/0x50 fs/namei.c:3036
 lookup_bdev+0xd8/0x2a0 block/bdev.c:1268
 bdev_file_open_by_path+0x82/0x330 block/bdev.c:1123
 add_device drivers/mtd/devices/block2mtd.c:279 [inline]
 block2mtd_setup2.isra.0+0x2ee/0xbd0 drivers/mtd/devices/block2mtd.c:459
 block2mtd_setup+0xbd/0xd0 drivers/mtd/devices/block2mtd.c:476
 param_attr_store+0x199/0x300 kernel/params.c:591
 module_attr_store+0x58/0x80 kernel/params.c:906
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe909d97479
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:00007fe90ab65028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fe909fc5fa0 RCX: 00007fe909d97479
RDX: 0000000000000003 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007fe909e281bc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe909fc5fa0 R15: 00007ffeab53b0a8
 </TASK>
block2mtd: error: cannot open device 3QI