[v6.1] general protection fault in gspca_init_transfer

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=145b9fb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=a4d1d00a1acef7aed3d3
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17ed8149580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/156843a60452/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/719d532a0151/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/12160bc2f9ec/bzImage-e4f7d8be.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a4d1d0...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 4820 Comm: syz.2.95 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:build_isoc_ep_tb drivers/media/usb/gspca/gspca.c:585 [inline]
RIP: 0010:gspca_init_transfer+0x5d2/0x2f60 drivers/media/usb/gspca/gspca.c:796
Code: 8b 44 24 70 89 84 24 b0 02 00 00 b8 01 00 00 00 48 89 44 24 28 4c 8b 6c 24 58 e9 41 0c 00 00 49 8d 5d 10 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 5a 28 00 00 8b 1b 83 fb 10 b8 10 00 00
RSP: 0018:ffffc90004a7f640 EFLAGS: 00010202
RAX: 0000000000000002 RBX: 0000000000000010 RCX: 0000000000000000
RDX: ffff888029778000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90004a7f9f8 R08: ffffc90004a7f96f R09: ffffc90004a7f8f0
R10: dffffc0000000000 R11: fffff5200094ff2e R12: ffffffff86e9d850
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88805d6ca000
FS: 00007f76ba6ad6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055eb4e520660 CR3: 00000000777b5000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
gspca_start_streaming+0x69/0x240 drivers/media/usb/gspca/gspca.c:1360
vb2_start_streaming+0x118/0x4a0 drivers/media/common/videobuf2/videobuf2-core.c:1613
vb2_core_streamon+0x253/0x380 drivers/media/common/videobuf2/videobuf2-core.c:2148
__vb2_init_fileio+0x980/0xc60 drivers/media/common/videobuf2/videobuf2-core.c:2729
__vb2_perform_fileio+0x346/0x1590 drivers/media/common/videobuf2/videobuf2-core.c:2805
vb2_fop_read+0x22e/0x340 drivers/media/common/videobuf2/videobuf2-v4l2.c:1174
v4l2_read+0x193/0x2b0 drivers/media/v4l2-core/v4l2-dev.c:314
vfs_read+0x2db/0x960 fs/read_write.c:468
ksys_read+0x14d/0x260 fs/read_write.c:613
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f76b979e0d9
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:00007f76ba6ad028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f76b9a26090 RCX: 00007f76b979e0d9
RDX: 0000000000001000 RSI: 0000200000000600 RDI: 0000000000000006
RBP: 00007f76b9835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f76b9a26128 R14: 00007f76b9a26090 R15: 00007ffd2eea9f88
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:build_isoc_ep_tb drivers/media/usb/gspca/gspca.c:585 [inline]
RIP: 0010:gspca_init_transfer+0x5d2/0x2f60 drivers/media/usb/gspca/gspca.c:796
Code: 8b 44 24 70 89 84 24 b0 02 00 00 b8 01 00 00 00 48 89 44 24 28 4c 8b 6c 24 58 e9 41 0c 00 00 49 8d 5d 10 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 5a 28 00 00 8b 1b 83 fb 10 b8 10 00 00
RSP: 0018:ffffc90004a7f640 EFLAGS: 00010202
RAX: 0000000000000002 RBX: 0000000000000010 RCX: 0000000000000000
RDX: ffff888029778000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90004a7f9f8 R08: ffffc90004a7f96f R09: ffffc90004a7f8f0
R10: dffffc0000000000 R11: fffff5200094ff2e R12: ffffffff86e9d850
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88805d6ca000
FS: 00007f76ba6ad6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055eb4e520660 CR3: 00000000777b5000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 8b 44 24 70 mov 0x70(%rsp),%eax
4: 89 84 24 b0 02 00 00 mov %eax,0x2b0(%rsp)
b: b8 01 00 00 00 mov $0x1,%eax
10: 48 89 44 24 28 mov %rax,0x28(%rsp)
15: 4c 8b 6c 24 58 mov 0x58(%rsp),%r13
1a: e9 41 0c 00 00 jmp 0xc60
1f: 49 8d 5d 10 lea 0x10(%r13),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 30 movzbl (%rax,%r14,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 5a 28 00 00 jne 0x2891
37: 8b 1b mov (%rbx),%ebx
39: 83 fb 10 cmp $0x10,%ebx
3c: b8 .byte 0xb8
3d: 10 00 adc %al,(%rax)


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