WARNING in dummy_free_request

Status: upstream: reported on 2026/09/02 22:03
Reported-by: syzbot+7c9dad99cc5b056c1d3a@syzkaller.appspotmail.com
First crash: 16d, last: 16d
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in dummy_free_request usb -1 1 2407d 2401d 0/29 closed as invalid on 2020/02/24 16:14
upstream WARNING in dummy_free_request (2) prio:normal usb -1 syz, C error 15 1d19h 52d 0/29 upstream: reported C repro on 2026/07/29 00:10
linux-6.1 WARNING in dummy_free_request -1 syz, C 6 26d 49d 0/3 upstream: reported C repro on 2026/07/31 20:31

Sample crash report:
gadgetfs: disconnected
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4499 at drivers/usb/gadget/udc/dummy_hcd.c:706 dummy_free_request+0x63/0x70 drivers/usb/gadget/udc/dummy_hcd.c:706
Modules linked in:
CPU: 0 PID: 4499 Comm: syz.0.23 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:dummy_free_request+0x63/0x70 drivers/usb/gadget/udc/dummy_hcd.c:706
Code: 87 fb 48 8b 03 48 39 d8 75 1b e8 a8 b1 42 fb 48 89 df 5b 41 5e e9 dd 4a 87 fb e8 98 b1 42 fb 0f 0b 5b 41 5e c3 e8 8d b1 42 fb <0f> 0b eb e1 66 0f 1f 84 00 00 00 00 00 55 41 57 41 56 41 55 41 54
RSP: 0018:ffffc90004b47cf8 EFLAGS: 00010293
RAX: ffffffff86365e13 RBX: ffff88807a320300 RCX: ffff888022289dc0
RDX: 0000000000000000 RSI: ffff88807a320310 RDI: ffff888147a84068
RBP: 1ffff11028f5098b R08: ffffffff8d8b122f R09: 1ffffffff1b16245
R10: dffffc0000000000 R11: fffffbfff1b16246 R12: ffff888147a84068
R13: dffffc0000000000 R14: ffff888147a84068 R15: ffff88807a320310
FS:  000055557b3c5500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32705450 CR3: 000000001f895000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 gadgetfs_unbind+0x1a5/0x2a0 drivers/usb/gadget/legacy/inode.c:1659
 usb_gadget_remove_driver+0x15c/0x350 drivers/usb/gadget/udc/core.c:1495
 usb_gadget_unregister_driver+0x15d/0x4c0 drivers/usb/gadget/udc/core.c:1654
 dev_release+0x82/0x1f0 drivers/usb/gadget/legacy/inode.c:1197
 __fput+0x212/0x8c0 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe677477159
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:00007ffec956d5b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffec956d6a0 RCX: 00007fe677477159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000134a6 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b31420000 R11: 0000000000000246 R12: 00007ffec956d6e0
R13: 00007fe6776fefac R14: 0000000000013ee8 R15: 00007fe6776fefa0
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/02 22:02 linux-5.15.y 0996e0926f6b 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING in dummy_free_request
* Struck through repros no longer work on HEAD.