======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.7.3509/6576 is trying to acquire lock:
ffff888105ffc460 (sb_writers#20){++++}-{0:0}, at: mnt_want_write+0x41/0x90

but task is already holding lock:
ffff8881173f5920 (&common->filesem){+.+.}-{4:4}, at: fsg_store_file+0x163/0x400

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&common->filesem){+.+.}-{4:4}:
       down_write+0x96/0x200
       fsg_store_file+0x163/0x400
       configfs_write_iter+0x337/0x430
       vfs_write+0x612/0xba0
       ksys_write+0x150/0x270
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&p->frag_sem){++++}-{4:4}:
       down_read+0x4a/0x330
       __configfs_open_file+0xd8/0x7d0
       do_dentry_open+0x816/0x1380
       vfs_open+0x3b/0x340
       dentry_open+0x61/0xa0
       ima_calc_file_hash+0x15f/0x890
       ima_collect_measurement+0x51b/0xa00
       process_measurement+0x1272/0x1c10
       ima_file_check+0xe1/0x130
       security_file_post_open+0xb3/0x260
       path_openat+0x1485/0x1d60
       do_file_open+0x23e/0x4a0
       do_sys_openat2+0x115/0x200
       __x64_sys_openat+0x138/0x170
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       process_measurement+0x7d0/0x1c10
       ima_file_check+0xe1/0x130
       security_file_post_open+0xb3/0x260
       path_openat+0x1485/0x1d60
       do_file_open+0x23e/0x4a0
       do_sys_openat2+0x115/0x200
       __x64_sys_open+0x11e/0x150
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_writers#20){++++}-{0:0}:
       __lock_acquire+0x1520/0x2cf0
       lock_acquire+0x106/0x350
       sb_start_write+0x4d/0x1c0
       mnt_want_write+0x41/0x90
       lookup_open+0x1e6/0x1a40
       path_openat+0x677/0x1d60
       do_file_open+0x23e/0x4a0
       filp_open+0x16d/0x1d0
       fsg_lun_open+0x6c/0xdf0
       fsg_store_file+0x19e/0x400
       configfs_write_iter+0x337/0x430
       vfs_write+0x612/0xba0
       ksys_write+0x150/0x270
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  sb_writers#20 --> &p->frag_sem --> &common->filesem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&common->filesem);
                               lock(&p->frag_sem);
                               lock(&common->filesem);
  rlock(sb_writers#20);

 *** DEADLOCK ***

5 locks held by syz.7.3509/6576:
 #0: ffff8881bdffa8f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff88810231e460 (sb_writers#22){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffff8881734b0080 (&buffer->mutex#2){+.+.}-{4:4}, at: configfs_write_iter+0x7e/0x430
 #3: ffff8881116a6070 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x238/0x430
 #4: ffff8881173f5920 (&common->filesem){+.+.}-{4:4}, at: fsg_store_file+0x163/0x400

stack backtrace:
CPU: 1 UID: 0 PID: 6576 Comm: syz.7.3509 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x1520/0x2cf0
 lock_acquire+0x106/0x350
 sb_start_write+0x4d/0x1c0
 mnt_want_write+0x41/0x90
 lookup_open+0x1e6/0x1a40
 path_openat+0x677/0x1d60
 do_file_open+0x23e/0x4a0
 filp_open+0x16d/0x1d0
 fsg_lun_open+0x6c/0xdf0
 fsg_store_file+0x19e/0x400
 configfs_write_iter+0x337/0x430
 vfs_write+0x612/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd1e2f9e019
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:00007fd1e3d88028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd1e3225fa0 RCX: 00007fd1e2f9e019
RDX: 0000000000000002 RSI: 0000200000000f00 RDI: 0000000000000007
RBP: 00007fd1e303500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd1e3226038 R14: 00007fd1e3225fa0 R15: 00007ffeba4c29d8
 </TASK>
mass_storage.usb0/lun.0: unable to open backing file: fi
