Re: [syzbot] [usb?] general protection fault in keyspan_break_ctl

[Johan Hovold]

On Thu, Aug 27, 2026 at 11:53:24AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    818bebeb63dd drm/xe: Don't hand out the flat CCS storage a..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16ba2979580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ccca94d2c01b9e78
> dashboard link: https://syzkaller.appspot.com/bug?extid=473d7477c523b41d4046
> 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=161f499e580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-818bebeb.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6e4100526b12/vmlinux-818bebeb.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/723c4783ee96/bzImage-818bebeb.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+473d7477c523b41d4046@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000013: 0000 [#1] SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f]
> CPU: 2 UID: 0 PID: 6029 Comm: syz.3.20 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:keyspan_break_ctl+0x8e/0xe0 drivers/usb/serial/keyspan.c:608
> Code: ff ff ff e8 54 ca 48 fa 83 fb ff 48 b8 00 00 00 00 00 fc ff df 49 8d bc 24 9c 00 00 00 0f 94 c3 48 89 fa 0f b6 db 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 1d 41
> RSP: 0018:ffffc900035b7cb0 EFLAGS: 00010203
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff87c231ec
> RDX: 0000000000000013 RSI: 00000000ffffffff RDI: 000000000000009c
> RBP: ffff88802f436000 R08: 0000000000000005 R09: 00000000ffffffff
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: ffff888034d39020 R14: ffff888034d390c8 R15: 0000000000000000
> FS:  0000555589f16500(0000) GS:ffff8880d5da2000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f5bac070000 CR3: 00000000584fe000 CR4: 0000000000352ef0
> Call Trace:
>  <TASK>
>  serial_break+0xcb/0x160 drivers/usb/serial/usb-serial.c:538
>  send_break drivers/tty/tty_io.c:2458 [inline]
>  send_break+0x2ec/0x370 drivers/tty/tty_io.c:2441
>  tty_ioctl+0xa2c/0x1640 drivers/tty/tty_io.c:2733
>  vfs_ioctl fs/ioctl.c:51 [inline]

And this is most likely the known issue I've promised to produce a patch
for:

	https://lore.kernel.org/all/ZIGejjOfsWkwjB2s@xxxxxxxxxxxxxxxxxxxx/

I'll revisit the fix and post it now...

Johan