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

[syzbot <syzbot+6665d3db5fef15914802@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    bd5f485f3f02 Merge tag 'soc-arm-7.3' of git://git.kernel.o..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16736e79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6d6c2a05eaadaf10
dashboard link: https://syzkaller.appspot.com/bug?extid=6665d3db5fef15914802
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=133f2549580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2da33ef8d789/disk-bd5f485f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7e8921e0c1e1/vmlinux-bd5f485f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c7e5335b79c8/bzImage-bd5f485f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6665d3db5fef15914802@syzkaller.appspotmail.com

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in net/atm/common.c:381:10
shift exponent -1 is negative
CPU: 0 UID: 0 PID: 6073 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x279/0x2a0 lib/ubsan.c:494
 __vcc_connect net/atm/common.c:381 [inline]
 vcc_connect.cold+0xe0/0x123 net/atm/common.c:498
 pvc_bind+0x33f/0x460 net/atm/pvc.c:52
 __sys_bind_socket net/socket.c:1945 [inline]
 __sys_bind_socket net/socket.c:1937 [inline]
 __sys_bind+0x1a9/0x260 net/socket.c:1976
 __do_sys_bind net/socket.c:1981 [inline]
 __se_sys_bind net/socket.c:1979 [inline]
 __x64_sys_bind+0x72/0xb0 net/socket.c:1979
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6a3099e0d9
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:00007fff44bcea08 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007f6a30c25fa0 RCX: 00007f6a3099e0d9
RDX: 000000000000000c RSI: 0000200000000100 RDI: 0000000000000004
RBP: 00007f6a30a35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6a30c25fac R14: 00007f6a30c25fa0 R15: 00007f6a30c25fa0
 </TASK>
---[ end trace ]---


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup