[v5.15] general protection fault in dummy_queue

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6e2fd6534337 Linux 5.15.213
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13567cc6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=2ee87a9a2213762be962
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d7b46606b13d/disk-6e2fd653.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/da120fdeb081/vmlinux-6e2fd653.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c2643457e3f/bzImage-6e2fd653.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2ee87a...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 0 PID: 4747 Comm: syz.0.166 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:dummy_queue+0x1a2/0x850 drivers/usb/gadget/udc/dummy_hcd.c:714
Code: fc ff df 80 3c 08 00 74 08 4c 89 e7 e8 67 87 87 fb 4d 8b 24 24 49 83 c4 60 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 80 05 00 00 45 8b 24 24 44 89 e6 83 e6 02
RSP: 0018:ffffc9000326f9a8 EFLAGS: 00010206
RAX: 000000000000000c RBX: ffff888061614c10 RCX: dffffc0000000000
RDX: 0000000000000002 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 1ffff1100c2c2980 R08: ffff88801adc000b R09: 1ffff110035b8001
R10: dffffc0000000000 R11: ffffed10035b8002 R12: 0000000000000060
R13: ffff888061614c00 R14: ffff8880231740e0 R15: ffff888023174c00
FS: 00007fd5049d56c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd5049d3fd8 CR3: 000000005fe8d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
usb_ep_queue+0xe6/0x350 drivers/usb/gadget/udc/core.c:288
raw_process_ep_io+0x5f7/0xc80 drivers/usb/gadget/legacy/raw_gadget.c:1061
raw_ioctl_ep_write drivers/usb/gadget/legacy/raw_gadget.c:1101 [inline]
raw_ioctl+0x20f7/0x3750 drivers/usb/gadget/legacy/raw_gadget.c:1274
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
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: 0033:0x7fd50679dd6b
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007fd5049d3f60 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000040 RCX: 00007fd50679dd6b
RDX: 00007fd5049d3fe0 RSI: 0000000040085507 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007fd506b50320 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000200000000300
R13: 0000000000000000 R14: 00007fd506a26090 R15: 00007ffc85bf9c58
</TASK>
Modules linked in:
---[ end trace 55bc791c0987fbfa ]---
RIP: 0010:dummy_queue+0x1a2/0x850 drivers/usb/gadget/udc/dummy_hcd.c:714
Code: fc ff df 80 3c 08 00 74 08 4c 89 e7 e8 67 87 87 fb 4d 8b 24 24 49 83 c4 60 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 80 05 00 00 45 8b 24 24 44 89 e6 83 e6 02
RSP: 0018:ffffc9000326f9a8 EFLAGS: 00010206
RAX: 000000000000000c RBX: ffff888061614c10 RCX: dffffc0000000000
RDX: 0000000000000002 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 1ffff1100c2c2980 R08: ffff88801adc000b R09: 1ffff110035b8001
R10: dffffc0000000000 R11: ffffed10035b8002 R12: 0000000000000060
R13: ffff888061614c00 R14: ffff8880231740e0 R15: ffff888023174c00
FS: 00007fd5049d56c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32714ff8 CR3: 000000005fe8d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: fc cld
1: ff lcall (bad)
2: df 80 3c 08 00 74 filds 0x7400083c(%rax)
8: 08 4c 89 e7 or %cl,-0x19(%rcx,%rcx,4)
c: e8 67 87 87 fb call 0xfb878778
11: 4d 8b 24 24 mov (%r12),%r12
15: 49 83 c4 60 add $0x60,%r12
19: 4c 89 e0 mov %r12,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
27: fc ff df
* 2a: 0f b6 04 08 movzbl (%rax,%rcx,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 0f 85 80 05 00 00 jne 0x5b6
36: 45 8b 24 24 mov (%r12),%r12d
3a: 44 89 e6 mov %r12d,%esi
3d: 83 e6 02 and $0x2,%esi


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