possible deadlock in uvcg_extension_ba_source_id_store

Status: upstream: reported on 2026/09/01 14:43
Subsystems: fs
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+76d92b6236b6ff1fc991@syzkaller.appspotmail.com
First crash: 53d, last: 7h16m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
e77ab8dc repro-c Reproduced: ✅ ❓ possible deadlock in uvcg_extension_ba_source_id_store 2026/09/25 01:51 2026/09/25 01:51 2026/09/25 03:13 3c3cdf19
c4277bf2 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ possible deadlock in uvcg_extension_ba_source_id_store 2026/08/30 00:56 2026/08/30 00:56 2026/08/30 01:00 2f52988a
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [fs?] possible deadlock in uvcg_extension_ba_source_id_store 0 (1) 2026/09/01 14:43
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/25 03:13 12m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5fc5768c7ca92895ccd1de94dc521e5a55ae7896 report job log log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.1.2331/15970 is trying to acquire lock:
ffffffff91404be8 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_extension_ba_source_id_store+0xdb/0x430 drivers/usb/gadget/function/uvc_configfs.c:1046

but task is already holding lock:
ffff88802d6a9270 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
ffff88802d6a9270 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x218/0x4e0 fs/configfs/file.c:229

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&p->frag_sem){++++}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_write_killable+0x93/0x240 kernel/locking/rwsem.c:1643
       configfs_rmdir+0x3fa/0x950 fs/configfs/dir.c:1543
       vfs_rmdir fs/namei.c:5525 [inline]
       vfs_rmdir+0x328/0x8a0 fs/namei.c:5498
       filename_rmdir+0x31a/0x5c0 fs/namei.c:5582
       __do_sys_unlinkat fs/namei.c:5757 [inline]
       __se_sys_unlinkat fs/namei.c:5750 [inline]
       __x64_sys_unlinkat+0xf5/0x130 fs/namei.c:5750
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&sb->s_type->i_mutex_key#34){++++}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
       inode_lock include/linux/fs.h:1024 [inline]
       configfs_depend_item_unlocked+0xf3/0x6a0 fs/configfs/dir.c:1268
       usbg_make_tpg+0x251/0x610 drivers/usb/gadget/function/f_tcm.c:1692
       target_fabric_make_tpg+0xab/0x8c0 drivers/target/target_core_fabric_configfs.c:947
       configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369
       vfs_mkdir+0x364/0x850 fs/namei.c:5420
       filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453
       __do_sys_mkdirat fs/namei.c:5474 [inline]
       __se_sys_mkdirat fs/namei.c:5471 [inline]
       __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5471
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (tpg_instances_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+0x1a4/0x1c20 kernel/locking/mutex.c:821
       tcm_alloc_inst+0x5f/0x1e0 drivers/usb/gadget/function/f_tcm.c:2687
       try_get_usb_function_instance+0x136/0x1f0 drivers/usb/gadget/functions.c:28
       usb_get_function_instance+0x16/0x70 drivers/usb/gadget/functions.c:44
       function_make+0x18c/0x3f0 drivers/usb/gadget/configfs.c:626
       configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369
       vfs_mkdir+0x364/0x850 fs/namei.c:5420
       filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453
       __do_sys_mkdirat fs/namei.c:5474 [inline]
       __se_sys_mkdirat fs/namei.c:5471 [inline]
       __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5471
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (func_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+0x1a4/0x1c20 kernel/locking/mutex.c:821
       try_get_usb_function_instance+0x26/0x1f0 drivers/usb/gadget/functions.c:18
       usb_get_function_instance+0x16/0x70 drivers/usb/gadget/functions.c:44
       function_make+0x18c/0x3f0 drivers/usb/gadget/configfs.c:626
       configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369
       vfs_mkdir+0x364/0x850 fs/namei.c:5420
       filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453
       __do_sys_mkdirat fs/namei.c:5474 [inline]
       __se_sys_mkdirat fs/namei.c:5471 [inline]
       __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5471
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (gadget_subsys.su_mutex){+.+.}-{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
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821
       uvcg_extension_ba_source_id_store+0xdb/0x430 drivers/usb/gadget/function/uvc_configfs.c:1046
       flush_write_buffer fs/configfs/file.c:207 [inline]
       configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
       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+0x123/0x790 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:
  gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#34 --> &p->frag_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&p->frag_sem);
                               lock(&sb->s_type->i_mutex_key#34);
                               lock(&p->frag_sem);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

locks held by syz.1.2331/15970: 4, last CPU#0:
 #0: ffff88807b9d5eb0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1408
 #1: ffff88801f77c460 (sb_writers#20){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffff888069e5de80 (&buffer->mutex){+.+.}-{4:4}, at: configfs_write_iter+0x76/0x4e0 fs/configfs/file.c:226
 #3: ffff88802d6a9270 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
 #3: ffff88802d6a9270 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x218/0x4e0 fs/configfs/file.c:229

stack backtrace:
CPU: 0 UID: 0 PID: 15970 Comm: syz.1.2331 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
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
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821
 uvcg_extension_ba_source_id_store+0xdb/0x430 drivers/usb/gadget/function/uvc_configfs.c:1046
 flush_write_buffer fs/configfs/file.c:207 [inline]
 configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
 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+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f38c179f559
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:00007f38c2738028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f38c1a25fa0 RCX: 00007f38c179f559
RDX: 0000000000000032 RSI: 0000200000000bc0 RDI: 0000000000000006
RBP: 00007f38c1836b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f38c1a26038 R14: 00007f38c1a25fa0 R15: 00007ffcaf7cf188
 </TASK>

Crashes (16):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/20 14:49 upstream f47d223627f8 df8746fb .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root possible deadlock in uvcg_extension_ba_source_id_store
2026/10/18 15:01 upstream 32c52ec87d62 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root possible deadlock in uvcg_extension_ba_source_id_store
2026/10/14 16:11 upstream 4056b3c9d3c9 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in uvcg_extension_ba_source_id_store
2026/10/13 20:21 upstream 24a19b953e2a 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in uvcg_extension_ba_source_id_store
2026/10/08 10:12 upstream 7b63ef2d55f2 4f6a9fcf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in uvcg_extension_ba_source_id_store
2026/10/08 07:48 upstream 7b63ef2d55f2 4f6a9fcf .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in uvcg_extension_ba_source_id_store
2026/08/28 14:37 upstream 818bebeb63dd 41d151d4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in uvcg_extension_ba_source_id_store
2026/10/09 03:01 upstream 6c377d19d4a5 b2734a59 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in uvcg_extension_ba_source_id_store
2026/09/29 10:12 upstream 72d3fcf802c4 7bf4ea23 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in uvcg_extension_ba_source_id_store
2026/08/29 02:03 upstream 548e7bcd0c54 2f52988a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in uvcg_extension_ba_source_id_store
2026/10/14 15:46 linux-next 1fffefb00cc0 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in uvcg_extension_ba_source_id_store
2026/10/09 01:34 linux-next b01868671970 b2734a59 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in uvcg_extension_ba_source_id_store
2026/09/29 05:19 linux-next 6375e61c01e9 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in uvcg_extension_ba_source_id_store
2026/09/29 04:56 linux-next 6375e61c01e9 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in uvcg_extension_ba_source_id_store
2026/09/26 11:51 linux-next f5f84daefcd9 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in uvcg_extension_ba_source_id_store
2026/09/06 04:11 linux-next 9d80aa4617b3 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in uvcg_extension_ba_source_id_store
* Struck through repros no longer work on HEAD.