[syzbot] [net?] [usb?] UBSAN: shift-out-of-bounds in __vcc_connect

[syzbot <syzbot+f6ac161ee9699270b8dd@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    26260251022f Merge tag 'livepatching-for-7.3' of git://git..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14fa5179580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a70bec3546180b6
dashboard link: https://syzkaller.appspot.com/bug?extid=f6ac161ee9699270b8dd
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=12698625580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/858149e586b7/disk-26260251.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8c4a5ad34e66/vmlinux-26260251.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fa4efe98315e/bzImage-26260251.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f6ac161ee9699270b8dd@syzkaller.appspotmail.com

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in net/atm/common.c:382:32
shift exponent -1 is negative
CPU: 0 UID: 0 PID: 5987 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
 __vcc_connect+0x14b4/0x19c0 net/atm/common.c:382
 vcc_connect+0x328/0x8f0 net/atm/common.c:498
 pvc_bind+0x272/0x380 net/atm/pvc.c:52
 __sys_bind_socket net/socket.c:1945 [inline]
 __sys_bind+0x2e3/0x410 net/socket.c:1976
 __do_sys_bind net/socket.c:1981 [inline]
 __se_sys_bind net/socket.c:1979 [inline]
 __x64_sys_bind+0x7a/0x90 net/socket.c:1979
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc16739e0d9
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:00007fff0c105ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007fc167625fa0 RCX: 00007fc16739e0d9
RDX: 000000000000000c RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007fc167435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc167625fac R14: 00007fc167625fa0 R15: 00007fc167625fa0
 </TASK>
---[ end trace ]---


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