WARNING in dummy_free_request (2)

Status: upstream: reported C repro on 2026/07/29 00:10
Subsystems: usb
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+c73e1942197af9f54ca3@syzkaller.appspotmail.com
First crash: 22d, last: 2d10h
✨ AI Patch Versions (1)
Version Stage Reported Report Link Job
1 moderation 2026/08/02 21:15 Discussion e95b2737-0582-4db2-9c86-a70a9a1e16cc
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
e95b2737 patching WARNING in dummy_free_request (2) 2026/08/02 19:13 2026/08/02 19:20 2026/08/02 21:15 e611ffe1
a52d103a assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in dummy_free_request (2) 2026/07/26 00:00 2026/07/26 00:00 2026/07/26 00:51 492bab15
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [usb?] WARNING in dummy_free_request (2) 0 (2) 2026/08/02 00:10
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in dummy_free_request usb -1 1 2373d 2367d 0/29 closed as invalid on 2020/02/24 16:14
linux-6.1 WARNING in dummy_free_request -1 syz, C 5 3d16h 15d 0/3 upstream: reported C repro on 2026/07/31 20:31

Sample crash report:
gadgetfs: suspended from state 3
gadgetfs: disconnected
------------[ cut here ]------------
!list_empty(&req->queue)
WARNING: drivers/usb/gadget/udc/dummy_hcd.c:710 at dummy_free_request+0x6f/0x80 drivers/usb/gadget/udc/dummy_hcd.c:710, CPU#1: syz-executor587/5718
Modules linked in:
CPU: 1 UID: 0 PID: 5718 Comm: syz-executor587 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:dummy_free_request+0x6f/0x80 drivers/usb/gadget/udc/dummy_hcd.c:710
Code: 75 22 e8 d4 98 99 fa 48 89 df 5b 41 5e e9 39 38 f7 fa e8 c4 98 99 fa 90 0f 0b 90 5b 41 5e c3 cc cc cc cc cc e8 b2 98 99 fa 90 <0f> 0b 90 eb d8 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc90004717bf0 EFLAGS: 00010293
RAX: ffffffff872c2f7e RBX: ffff888043ad0000 RCX: ffff888031938000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 1ffff11003df0993 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff872c2f10 R12: ffff88801ef840a8
R13: dffffc0000000000 R14: ffff88801ef840a8 R15: ffff888043ad0010
FS:  000055557d671400(0000) GS:ffff888125d46000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f11655c40fc CR3: 0000000044e6e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 gadgetfs_unbind+0x1b2/0x2c0 drivers/usb/gadget/legacy/inode.c:1661
 gadget_unbind_driver+0x1cb/0x410 drivers/usb/gadget/udc/core.c:1724
 device_remove drivers/base/dd.c:616 [inline]
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
 driver_detach+0x1f3/0x2d0 drivers/base/dd.c:1435
 bus_remove_driver+0x229/0x320 drivers/base/bus.c:832
 usb_gadget_unregister_driver+0x4e/0x70 drivers/usb/gadget/udc/core.c:1784
 dev_release+0x86/0x210 drivers/usb/gadget/legacy/inode.c:1198
 __fput+0x42a/0xa80 fs/file_table.c:512
 fput_close_sync+0x11f/0x240 fs/file_table.c:617
 __do_sys_close fs/open.c:1511 [inline]
 __se_sys_close fs/open.c:1496 [inline]
 __x64_sys_close+0x7e/0x110 fs/open.c:1496
 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: 0033:0x7f116556dad7
Code: 48 89 fa 4c 89 df e8 48 1f 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffe7ccdb7c0 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 000055557d671400 RCX: 00007f116556dad7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffe7ccdb860
R13: 0000000000025768 R14: 00007ffe7ccdb82c R15: 00007ffe7ccdb840
 </TASK>

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/13 13:15 upstream 3d6d817622b0 359b2492 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in dummy_free_request
2026/08/13 00:16 upstream 3d6d817622b0 359b2492 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in dummy_free_request
2026/08/12 10:18 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci f9054278acf4 f8d35649 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in dummy_free_request
2026/08/02 00:09 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e2d5e23967d0 e611ffe1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in dummy_free_request
2026/08/05 09:49 upstream 562bfb501c54 52aa2820 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in dummy_free_request
2026/08/02 18:38 upstream 2d2338c93da7 e611ffe1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in dummy_free_request
2026/08/01 15:32 upstream 02dc699f83d0 e611ffe1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in dummy_free_request
2026/08/06 23:54 linux-next 1701fda2f58e c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in dummy_free_request
2026/08/06 23:45 linux-next 1701fda2f58e c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in dummy_free_request
2026/07/24 20:10 linux-next cc2b5f627e8c 05b26a28 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in dummy_free_request
2026/08/01 23:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e2d5e23967d0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in dummy_free_request
2026/08/01 23:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e2d5e23967d0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in dummy_free_request
* Struck through repros no longer work on HEAD.