possible deadlock in __configfs_open_file

Status: upstream: reported syz repro on 2026/08/04 15:47
Reported-by: syzbot+b14a81296626e1c6e9e5@syzkaller.appspotmail.com
First crash: 51d, last: 23d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in __configfs_open_file (2) prio:low integrity lsm 4 30 15h05m 57d 0/29 upstream: reported on 2026/07/30 01:47
upstream possible deadlock in __configfs_open_file fs 4 syz, C 29 224d 642d 29/29 fixed on 2026/05/06 16:40
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/01 20:19 10m retest repro linux-5.15.y report job log log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.18/4329 is trying to acquire lock:
ffff88807deb1678 (&p->frag_sem){.+.+}-{3:3}, at: __configfs_open_file+0xd5/0x7d0 fs/configfs/file.c:304

but task is already holding lock:
ffff88802365fd38 (&iint_mutex_key[depth]){+.+.}-{3:3}, at: process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&iint_mutex_key[depth]){+.+.}-{3:3}:
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261
       ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533
       do_open fs/namei.c:3618 [inline]
       path_openat+0x27cf/0x2fb0 fs/namei.c:3750
       do_filp_open+0x1df/0x400 fs/namei.c:3777
       do_sys_openat2+0x14b/0x500 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_openat fs/open.c:1287 [inline]
       __se_sys_openat fs/open.c:1282 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1282
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (sb_writers#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_write+0x4f/0x1c0 include/linux/fs.h:1881
       mnt_want_write+0x3d/0x90 fs/namespace.c:386
       open_last_lookups fs/namei.c:3529 [inline]
       path_openat+0x795/0x2fb0 fs/namei.c:3747
       do_filp_open+0x1df/0x400 fs/namei.c:3777
       file_open_name fs/open.c:1200 [inline]
       filp_open+0x17c/0x1e0 fs/open.c:1220
       fsg_lun_open+0x63/0xee0 drivers/usb/gadget/function/storage_common.c:193
       fsg_store_file+0x1a5/0x530 drivers/usb/gadget/function/storage_common.c:454
       flush_write_buffer fs/configfs/file.c:207 [inline]
       configfs_write_iter+0x30b/0x400 fs/configfs/file.c:229
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x748/0xd70 fs/read_write.c:594
       ksys_write+0x153/0x260 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&common->filesem){+.+.}-{3:3}:
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       fsg_store_file+0x174/0x530 drivers/usb/gadget/function/storage_common.c:451
       flush_write_buffer fs/configfs/file.c:207 [inline]
       configfs_write_iter+0x30b/0x400 fs/configfs/file.c:229
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x748/0xd70 fs/read_write.c:594
       ksys_write+0x153/0x260 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&p->frag_sem){.+.+}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       __configfs_open_file+0xd5/0x7d0 fs/configfs/file.c:304
       do_dentry_open+0x7f7/0xf90 fs/open.c:826
       vfs_open fs/open.c:958 [inline]
       dentry_open+0xc6/0x120 fs/open.c:974
       ima_calc_file_hash+0x18c/0x1940 security/integrity/ima/ima_crypto.c:558
       ima_collect_measurement+0x335/0x7e0 security/integrity/ima/ima_api.c:255
       process_measurement+0x1185/0x1c20 security/integrity/ima/ima_main.c:351
       ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533
       do_open fs/namei.c:3618 [inline]
       path_openat+0x27cf/0x2fb0 fs/namei.c:3750
       do_filp_open+0x1df/0x400 fs/namei.c:3777
       do_sys_openat2+0x14b/0x500 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_openat fs/open.c:1287 [inline]
       __se_sys_openat fs/open.c:1282 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1282
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &p->frag_sem --> sb_writers#3 --> &iint_mutex_key[depth]

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&iint_mutex_key[depth]);
                               lock(sb_writers#3);
                               lock(&iint_mutex_key[depth]);
  lock(&p->frag_sem);

 *** DEADLOCK ***

1 lock held by syz.0.18/4329:
 #0: ffff88802365fd38 (&iint_mutex_key[depth]){+.+.}-{3:3}, at: process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261

stack backtrace:
CPU: 0 PID: 4329 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
 __configfs_open_file+0xd5/0x7d0 fs/configfs/file.c:304
 do_dentry_open+0x7f7/0xf90 fs/open.c:826
 vfs_open fs/open.c:958 [inline]
 dentry_open+0xc6/0x120 fs/open.c:974
 ima_calc_file_hash+0x18c/0x1940 security/integrity/ima/ima_crypto.c:558
 ima_collect_measurement+0x335/0x7e0 security/integrity/ima/ima_api.c:255
 process_measurement+0x1185/0x1c20 security/integrity/ima/ima_main.c:351
 ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533
 do_open fs/namei.c:3618 [inline]
 path_openat+0x27cf/0x2fb0 fs/namei.c:3750
 do_filp_open+0x1df/0x400 fs/namei.c:3777
 do_sys_openat2+0x14b/0x500 fs/open.c:1255
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_openat fs/open.c:1287 [inline]
 __se_sys_openat fs/open.c:1282 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1282
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7faa94c1e0d9
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:00007fff37723298 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007faa94ea5fa0 RCX: 00007faa94c1e0d9
RDX: 0000000000000001 RSI: 0000200000000e00 RDI: ffffffffffffff9c
RBP: 00007faa94cb5024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faa94ea5fac R14: 00007faa94ea5fa0 R15: 00007faa94ea5fa0
 </TASK>
mass_storage.usb0/lun.0: unable to open backing file: f
ima: policy update completed

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/11 07:04 linux-5.15.y aabd761612db 508909ea .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in __configfs_open_file
2026/08/04 15:47 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in __configfs_open_file
* Struck through repros no longer work on HEAD.