[syzbot] [fs?] possible deadlock in uvcg_mjpeg_bma_controls_show

Hello,

syzbot found the following issue on:

HEAD commit:    8d3ae59288f1 Linux 7.2
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b1d69e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2ca5f2f2c4197664
dashboard link: https://syzkaller.appspot.com/bug?extid=2b082cefcfb1439289ef
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79f5b21ede1d/disk-8d3ae592.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0f43313295ab/vmlinux-8d3ae592.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5de229a3986e/bzImage-8d3ae592.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.9.535/9115 is trying to acquire lock:
ffffffff8f9eb768 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
ffffffff8f9eb768 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635

but task is already holding lock:
ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline]
ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x1cc/0x620 fs/configfs/file.c:88

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->frag_sem){++++}-{4:4}:
       down_write_killable+0xa6/0x240 kernel/locking/rwsem.c:1643
       configfs_rmdir+0x3b0/0x950 fs/configfs/dir.c:1534
       vfs_rmdir+0x3e6/0x6a0 fs/namei.c:5381
       filename_rmdir+0x292/0x520 fs/namei.c:5438
       __do_sys_unlinkat fs/namei.c:5613 [inline]
       __se_sys_unlinkat+0x71/0x1a0 fs/namei.c:5606
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&sb->s_type->i_mutex_key#27){++++}-{4:4}:
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       inode_lock include/linux/fs.h:1024 [inline]
       configfs_depend_item_unlocked+0x153/0x420 fs/configfs/dir.c:1259
       usbg_make_tpg+0x1f6/0x590 drivers/usb/gadget/function/f_tcm.c:1686
       target_fabric_make_tpg+0xa8/0x6d0 drivers/target/target_core_fabric_configfs.c:939
       configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x406/0x620 fs/namei.c:5276
       filename_mkdirat+0x285/0x510 fs/namei.c:5309
       __do_sys_mkdirat fs/namei.c:5330 [inline]
       __se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&opts->dep_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tcm_set_name+0x2b/0xd0 drivers/usb/gadget/function/f_tcm.c:2669
       function_make+0x1a8/0x360 drivers/usb/gadget/configfs.c:636
       configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x406/0x620 fs/namei.c:5276
       filename_mkdirat+0x285/0x510 fs/namei.c:5309
       __do_sys_mkdirat fs/namei.c:5330 [inline]
       __se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}:
       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+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
       uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635
       fill_read_buffer fs/configfs/file.c:68 [inline]
       configfs_read_iter+0x2b7/0x620 fs/configfs/file.c:88
       __kernel_read+0x4ca/0x960 fs/read_write.c:532
       integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
       ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
       ima_calc_file_hash+0x451/0x890 security/integrity/ima/ima_crypto.c:280
       ima_collect_measurement+0x51b/0xa00 security/integrity/ima/ima_api.c:300
       process_measurement+0x1272/0x1c10 security/integrity/ima/ima_main.c:425
       ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
       security_file_post_open+0xb3/0x260 security/security.c:2755
       do_open fs/namei.c:4702 [inline]
       path_openat+0x2e90/0x3830 fs/namei.c:4863
       do_file_open+0x23e/0x4a0 fs/namei.c:4892
       do_sys_openat2+0x115/0x200 fs/open.c:1368
       do_sys_open fs/open.c:1374 [inline]
       __do_sys_openat fs/open.c:1390 [inline]
       __se_sys_openat fs/open.c:1385 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1385
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 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:
  gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#27 --> &p->frag_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&p->frag_sem);
                               lock(&sb->s_type->i_mutex_key#27);
                               lock(&p->frag_sem);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

3 locks held by syz.9.535/9115:
 #0: ffff88807ddab480 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: process_measurement+0x7d0/0x1c10 security/integrity/ima/ima_main.c:319
 #1: ffff88801f7dd080 (&buffer->mutex){+.+.}-{4:4}, at: configfs_read_iter+0x70/0x620 fs/configfs/file.c:86
 #2: ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline]
 #2: ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x1cc/0x620 fs/configfs/file.c:88

stack backtrace:
CPU: 0 UID: 0 PID: 9115 Comm: syz.9.535 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
 uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635
 fill_read_buffer fs/configfs/file.c:68 [inline]
 configfs_read_iter+0x2b7/0x620 fs/configfs/file.c:88
 __kernel_read+0x4ca/0x960 fs/read_write.c:532
 integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
 ima_calc_file_hash+0x451/0x890 security/integrity/ima/ima_crypto.c:280
 ima_collect_measurement+0x51b/0xa00 security/integrity/ima/ima_api.c:300
 process_measurement+0x1272/0x1c10 security/integrity/ima/ima_main.c:425
 ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
 security_file_post_open+0xb3/0x260 security/security.c:2755
 do_open fs/namei.c:4702 [inline]
 path_openat+0x2e90/0x3830 fs/namei.c:4863
 do_file_open+0x23e/0x4a0 fs/namei.c:4892
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1385
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc9faf9e0d9
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:00007fc9fbdd8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc9fb226180 RCX: 00007fc9faf9e0d9
RDX: 0000000000000002 RSI: 00002000000002c0 RDI: ffffffffffffff9c
RBP: 00007fc9fb035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc9fb226218 R14: 00007fc9fb226180 R15: 00007ffe7532db78
 </TASK>


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