possible deadlock in fifo_open (2)

Status: upstream: reported on 2026/08/29 19:42
Subsystems: usb
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+e6737343c72c2accf79e@syzkaller.appspotmail.com
First crash: 51d, last: 5d19h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
b5109d2d repro-c Reproduced: ✅ ❓ possible deadlock in fifo_open (2) 2026/10/13 20:11 2026/10/13 20:11 2026/10/13 22:06 7321cd29
f610d526 repro-c 💥 possible deadlock in fifo_open (2) 2026/10/11 10:25 2026/10/11 10:25 2026/10/11 13:30 4f92358f
5e8a1d00 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ possible deadlock in fifo_open (2) 2026/08/27 02:24 2026/08/27 02:24 2026/08/27 03:06 a2b77b9e
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [usb?] possible deadlock in fifo_open (2) 0 (1) 2026/08/29 19:42
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-44 possible deadlock in fifo_open 4 syz, C 696 2507d 2743d 0/2 public: reported C repro on 2019/04/12 00:00
android-414 possible deadlock in fifo_open 4 syz, C 586 2753d 2744d 0/1 public: reported C repro on 2019/04/11 00:00
upstream possible deadlock in fifo_open fs 4 syz, C 2097 2760d 3240d 0/29 closed as dup on 2017/12/12 21:25
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/10/13 22:07 13m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907 report job log log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.1.966/9591 is trying to acquire lock:
ffff88804b871460 (&pipe->mutex){+.+.}-{4:4}, at: fifo_open+0x139/0xb40 fs/pipe.c:1235

but task is already holding lock:
ffff888055a23120 (&common->filesem){++++}-{4:4}, at: fsg_store_file+0x193/0x450 drivers/usb/gadget/function/storage_common.c:452

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&common->filesem){++++}-{4:4}:
       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
       fsg_show_file+0x20/0x180 drivers/usb/gadget/function/storage_common.c:339
       fill_read_buffer fs/configfs/file.c:68 [inline]
       configfs_read_iter+0x426/0x6f0 fs/configfs/file.c:88
       __kernel_read+0x397/0xad0 fs/read_write.c:532
       integrity_kernel_read+0x7e/0xb0 security/integrity/iint.c:28
       ima_calc_file_hash_tfm+0x25e/0x350 security/integrity/ima/ima_crypto.c:222
       ima_calc_file_hash+0x1e3/0x380 security/integrity/ima/ima_crypto.c:280
       ima_collect_measurement+0x94f/0xb30 security/integrity/ima/ima_api.c:300
       process_measurement+0xdfe/0x2350 security/integrity/ima/ima_main.c:425
       ima_file_check+0xc3/0x110 security/integrity/ima/ima_main.c:685
       security_file_post_open+0xc4/0x210 security/security.c:2755
       do_open fs/namei.c:4868 [inline]
       path_openat+0x5cd/0x2440 fs/namei.c:5029
       do_file_open+0x20e/0x430 fs/namei.c:5058
       do_sys_openat2+0x10f/0x1e0 fs/open.c:1417
       do_sys_open fs/open.c:1423 [inline]
       __do_sys_openat fs/open.c:1439 [inline]
       __se_sys_openat fs/open.c:1434 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1434
       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 (&p->frag_sem){++++}-{4:4}:
       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
       __configfs_open_file+0xe8/0x9c0 fs/configfs/file.c:304
       do_dentry_open+0x6ab/0x14d0 fs/open.c:996
       vfs_open+0x82/0x3f0 fs/open.c:1101
       dentry_open+0x71/0xd0 fs/open.c:1124
       ima_calc_file_hash+0xe1/0x380 security/integrity/ima/ima_crypto.c:269
       ima_collect_measurement+0x94f/0xb30 security/integrity/ima/ima_api.c:300
       process_measurement+0xdfe/0x2350 security/integrity/ima/ima_main.c:425
       ima_file_check+0xc3/0x110 security/integrity/ima/ima_main.c:685
       security_file_post_open+0xc4/0x210 security/security.c:2755
       do_open fs/namei.c:4868 [inline]
       path_openat+0x5cd/0x2440 fs/namei.c:5029
       do_file_open+0x20e/0x430 fs/namei.c:5058
       do_sys_openat2+0x10f/0x1e0 fs/open.c:1417
       do_sys_open fs/open.c:1423 [inline]
       __do_sys_openat fs/open.c:1439 [inline]
       __se_sys_openat fs/open.c:1434 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1434
       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 (&ima_iint_mutex_key[depth]){+.+.}-{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
       process_measurement+0x5ab/0x2350 security/integrity/ima/ima_main.c:319
       ima_file_check+0xc3/0x110 security/integrity/ima/ima_main.c:685
       security_file_post_open+0xc4/0x210 security/security.c:2755
       do_open fs/namei.c:4868 [inline]
       path_openat+0x5cd/0x2440 fs/namei.c:5029
       do_file_open+0x20e/0x430 fs/namei.c:5058
       file_open_name+0x1c3/0x3e0 fs/open.c:1375
       filp_open+0x2e/0x50 fs/open.c:1392
       kernel_read_file_from_path_initns+0xec/0x240 fs/kernel_read_file.c:159
       fw_get_filesystem_firmware drivers/base/firmware_loader/main.c:549 [inline]
       _request_firmware+0x733/0x13c0 drivers/base/firmware_loader/main.c:873
       request_firmware+0x35/0x50 drivers/base/firmware_loader/main.c:948
       reg_reload_regdb+0x85/0x460 net/wireless/reg.c:1067
       genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2575
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline]
       netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1364
       netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1919
       sock_sendmsg_nosec net/socket.c:800 [inline]
       __sock_sendmsg net/socket.c:815 [inline]
       ____sys_sendmsg+0xa4d/0xbe0 net/socket.c:2713
       ___sys_sendmsg+0x190/0x1e0 net/socket.c:2767
       __sys_sendmsg+0x160/0x210 net/socket.c:2799
       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 (cb_lock){++++}-{4:4}:
       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
       genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
       netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline]
       netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1364
       netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1919
       sock_sendmsg_nosec net/socket.c:800 [inline]
       __sock_sendmsg net/socket.c:815 [inline]
       sock_sendmsg+0x394/0x410 net/socket.c:838
       splice_to_socket+0xb3c/0x11a0 fs/splice.c:884
       do_splice_from fs/splice.c:936 [inline]
       do_splice+0x109c/0x1fa0 fs/splice.c:1349
       __do_splice+0x33b/0x370 fs/splice.c:1431
       __do_sys_splice fs/splice.c:1634 [inline]
       __se_sys_splice fs/splice.c:1616 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1616
       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 (&pipe->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+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       fifo_open+0x139/0xb40 fs/pipe.c:1235
       do_dentry_open+0x6ab/0x14d0 fs/open.c:996
       vfs_open+0x82/0x3f0 fs/open.c:1101
       do_open fs/namei.c:4866 [inline]
       path_openat+0x19fa/0x2440 fs/namei.c:5029
       do_file_open+0x20e/0x430 fs/namei.c:5058
       file_open_name+0x1c3/0x3e0 fs/open.c:1375
       filp_open+0x2e/0x50 fs/open.c:1392
       fsg_lun_open+0x6b/0x7b0 drivers/usb/gadget/function/storage_common.c:194
       fsg_store_file+0x1e7/0x450 drivers/usb/gadget/function/storage_common.c:455
       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:
  &pipe->mutex --> &p->frag_sem --> &common->filesem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&common->filesem);
                               lock(&p->frag_sem);
                               lock(&common->filesem);
  lock(&pipe->mutex);

 *** DEADLOCK ***

locks held by syz.1.966/9591: 5, last CPU#3:
 #0: ffff8880377bfb30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888025552460 (sb_writers#21){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffff888037d86080 (&buffer->mutex#2){+.+.}-{4:4}, at: configfs_write_iter+0x76/0x4e0 fs/configfs/file.c:226
 #3: ffff888037824a70 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
 #3: ffff888037824a70 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x218/0x4e0 fs/configfs/file.c:229
 #4: ffff888055a23120 (&common->filesem){++++}-{4:4}, at: fsg_store_file+0x193/0x450 drivers/usb/gadget/function/storage_common.c:452

stack backtrace:
CPU: 3 UID: 0 PID: 9591 Comm: syz.1.966 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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+0x1a4/0x1bd0 kernel/locking/mutex.c:821
 fifo_open+0x139/0xb40 fs/pipe.c:1235
 do_dentry_open+0x6ab/0x14d0 fs/open.c:996
 vfs_open+0x82/0x3f0 fs/open.c:1101
 do_open fs/namei.c:4866 [inline]
 path_openat+0x19fa/0x2440 fs/namei.c:5029
 do_file_open+0x20e/0x430 fs/namei.c:5058
 file_open_name+0x1c3/0x3e0 fs/open.c:1375
 filp_open+0x2e/0x50 fs/open.c:1392
 fsg_lun_open+0x6b/0x7b0 drivers/usb/gadget/function/storage_common.c:194
 fsg_store_file+0x1e7/0x450 drivers/usb/gadget/function/storage_common.c:455
 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: 0033:0x7fc6a2f9e1d9
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:00007fc6a3d97028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc6a3225fa0 RCX: 00007fc6a2f9e1d9
RDX: 0000000000000005 RSI: 00002000000003c0 RDI: 0000000000000004
RBP: 00007fc6a3035888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc6a3226038 R14: 00007fc6a3225fa0 R15: 00007ffd11f8bc68
 </TASK>
mass_storage.0/lun.0: invalid file type: file0

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/10 04:12 upstream 3857c2fe5449 4f92358f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in fifo_open
2026/08/25 19:40 upstream 818bebeb63dd a9a1fc32 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in fifo_open
* Struck through repros no longer work on HEAD.