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

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

[syzbot]

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@syzkaller.appspotmail.com

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]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 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: 0033:0x7f5bac19e0d9
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:00007ffd93db7608 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5bac425fa0 RCX: 00007f5bac19e0d9
RDX: 0000000000000000 RSI: 0000000000005425 RDI: 0000000000000004
RBP: 00007f5bac235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5bac425fac R14: 00007f5bac425fa0 R15: 00007f5bac425fa0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
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
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	ff                   	ljmp   (bad)
   1:	e8 54 ca 48 fa       	call   0xfa48ca5a
   6:	83 fb ff             	cmp    $0xffffffff,%ebx
   9:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  10:	fc ff df
  13:	49 8d bc 24 9c 00 00 	lea    0x9c(%r12),%rdi
  1a:	00
  1b:	0f 94 c3             	sete   %bl
  1e:	48 89 fa             	mov    %rdi,%rdx
  21:	0f b6 db             	movzbl %bl,%ebx
  24:	48 c1 ea 03          	shr    $0x3,%rdx
* 28:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2c:	48 89 f8             	mov    %rdi,%rax
  2f:	83 e0 07             	and    $0x7,%eax
  32:	83 c0 03             	add    $0x3,%eax
  35:	38 d0                	cmp    %dl,%al
  37:	7c 04                	jl     0x3d
  39:	84 d2                	test   %dl,%dl
  3b:	75 1d                	jne    0x5a
  3d:	41                   	rex.B


---
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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@syzkaller.appspotmail.com
> 
> 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@hovoldconsulting.com/

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

Johan