[syzbot] [sound?] general protection fault in snd_scarlett2_controls_create

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c025f6cf4209 Add linux-next specific files for 20260303
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1347bb5a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=54b410fabe2a4318
dashboard link: https://syzkaller.appspot.com/bug?extid=8f29539ef9a1c8334f42
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12242b5a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=143f1b5a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e2497bde352d/disk-c025f6cf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/36827cb45429/vmlinux-c025f6cf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ebf1ed6bb73/bzImage-c025f6cf.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8f2953...@syzkaller.appspotmail.com

usb 1-1: 0:6 : does not exist
usb 1-1: 0:7 : does not exist
usb 1-1: 0:8 : does not exist
usb 1-1: 0:9 : does not exist
usb 1-1: 0:10 : does not exist
usb 1-1: Focusrite Scarlett Gen 3 Mixer Driver enabled (pid=0x8215); report any issues to https://github.com/geoffreybennett/scarlett-gen2/issues
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 1215 Comm: kworker/0:3 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:usb_endpoint_num include/uapi/linux/usb/ch9.h:479 [inline]
RIP: 0010:scarlett2_find_fc_interface sound/usb/mixer_scarlett2.c:8257 [inline]
RIP: 0010:scarlett2_init_private sound/usb/mixer_scarlett2.c:8291 [inline]
RIP: 0010:snd_scarlett2_controls_create+0x998/0x4f70 sound/usb/mixer_scarlett2.c:8680
Code: 10 4c 8d b2 48 02 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 ea 31 00 00 45 88 3e 4c 8d 73 02 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 48 8b 7c 24 38 0f 85 ea 31 00 00 45 0f b6 3e
RSP: 0018:ffffc90005abe4c0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888076018000 RSI: 00000000000000ff RDI: ffff888027a637a0
RBP: ffffc90005abe8d8 R08: ffffffff8cd90234 R09: ffffffff8cd90248
R10: dffffc0000000000 R11: fffffbfff20684b7 R12: dffffc0000000000
R13: ffff888027a6378a R14: 0000000000000002 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff888124ff5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005603857c86e0 CR3: 0000000035240000 CR4: 00000000003526f0
Call Trace:
<TASK>
snd_scarlett2_init+0x42f/0x6a0 sound/usb/mixer_scarlett2.c:9403
snd_usb_mixer_apply_create_quirk+0x15a8/0x1be0 sound/usb/mixer_quirks.c:4446
snd_usb_create_mixer+0x1b5d/0x2890 sound/usb/mixer.c:3641
usb_audio_probe+0x1874/0x2330 sound/usb/card.c:1033
usb_probe_interface+0x668/0xc90 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x267/0xaf0 drivers/base/dd.c:661
__driver_probe_device+0x18c/0x320 drivers/base/dd.c:803
driver_probe_device+0x4f/0x240 drivers/base/dd.c:833
__device_attach_driver+0x2d4/0x4c0 drivers/base/dd.c:961
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c5/0x450 drivers/base/dd.c:1033
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1088
bus_probe_device+0x12a/0x220 drivers/base/bus.c:574
device_add+0x7b6/0xb70 drivers/base/core.c:3689
usb_set_configuration+0x1a87/0x2110 drivers/usb/core/message.c:2208
usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
usb_probe_device+0x1c4/0x3b0 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x267/0xaf0 drivers/base/dd.c:661
__driver_probe_device+0x18c/0x320 drivers/base/dd.c:803
driver_probe_device+0x4f/0x240 drivers/base/dd.c:833
__device_attach_driver+0x2d4/0x4c0 drivers/base/dd.c:961
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c5/0x450 drivers/base/dd.c:1033
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1088
bus_probe_device+0x12a/0x220 drivers/base/bus.c:574
device_add+0x7b6/0xb70 drivers/base/core.c:3689
usb_new_device+0xa08/0x16f0 drivers/usb/core/hub.c:2695
hub_port_connect drivers/usb/core/hub.c:5567 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
port_event drivers/usb/core/hub.c:5871 [inline]
hub_event+0x2a1c/0x4f30 drivers/usb/core/hub.c:5953
process_one_work+0x963/0x1720 kernel/workqueue.c:3285
process_scheduled_works kernel/workqueue.c:3376 [inline]
worker_thread+0xb46/0x1140 kernel/workqueue.c:3457
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:usb_endpoint_num include/uapi/linux/usb/ch9.h:479 [inline]
RIP: 0010:scarlett2_find_fc_interface sound/usb/mixer_scarlett2.c:8257 [inline]
RIP: 0010:scarlett2_init_private sound/usb/mixer_scarlett2.c:8291 [inline]
RIP: 0010:snd_scarlett2_controls_create+0x998/0x4f70 sound/usb/mixer_scarlett2.c:8680
Code: 10 4c 8d b2 48 02 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 ea 31 00 00 45 88 3e 4c 8d 73 02 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 48 8b 7c 24 38 0f 85 ea 31 00 00 45 0f b6 3e
RSP: 0018:ffffc90005abe4c0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888076018000 RSI: 00000000000000ff RDI: ffff888027a637a0
RBP: ffffc90005abe8d8 R08: ffffffff8cd90234 R09: ffffffff8cd90248
R10: dffffc0000000000 R11: fffffbfff20684b7 R12: dffffc0000000000
R13: ffff888027a6378a R14: 0000000000000002 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff888124ff5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005603857c86e0 CR3: 0000000076b5e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 10 4c 8d b2 adc %cl,-0x4e(%rbp,%rcx,4)
4: 48 02 00 rex.W add (%rax),%al
7: 00 4c 89 f0 add %cl,-0x10(%rcx,%rcx,4)
b: 48 c1 e8 03 shr $0x3,%rax
f: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
14: 84 c0 test %al,%al
16: 0f 85 ea 31 00 00 jne 0x3206
1c: 45 88 3e mov %r15b,(%r14)
1f: 4c 8d 73 02 lea 0x2(%rbx),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 48 8b 7c 24 38 mov 0x38(%rsp),%rdi
36: 0f 85 ea 31 00 00 jne 0x3226
3c: 45 0f b6 3e movzbl (%r14),%r15d


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