------------[ cut here ]------------
WARNING: CPU: 2 PID: 6933 at drivers/tty/serial/serial_core.c:625 uart_write+0x2bf/0x3e0 drivers/tty/serial/serial_core.c:625
Modules linked in:
CPU: 2 PID: 6933 Comm: syz-executor.2 Not tainted 6.10.0-rc3-syzkaller-00044-g2ccbdf43d5e7 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:uart_write+0x2bf/0x3e0 drivers/tty/serial/serial_core.c:625
Code: 6f fc e9 4e ff ff ff e8 0f 70 95 fc 90 0f 0b 90 49 c7 c4 d2 ff ff ff e9 39 ff ff ff e8 fa 6f 95 fc 45 31 ff e8 f2 6f 95 fc 90 <0f> 0b 90 48 85 ed 74 8c e8 e4 6f 95 fc 4c 8d a5 08 01 00 00 4c 89
RSP: 0018:ffffc90007067a20 EFLAGS: 00010087
RAX: 000000000000cab4 RBX: ffff88801dcf8be8 RCX: ffffc9002a201000
RDX: 0000000000040000 RSI: ffffffff84f91fde RDI: ffff88801dcf8f48
RBP: ffffffff94d61bc0 R08: 0000000000000001 R09: fffff52000e0cf32
R10: 0000000000000003 R11: 000000000000000b R12: 0000000000000001
R13: 0000000000000009 R14: ffff888054914001 R15: 0000000000000287
FS:  0000000000000000(0000) GS:ffff88802c200000(0063) knlGS:00000000f5f1bb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000020a1a000 CR3: 000000006726c000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ppp_async_push+0x89e/0x1740 drivers/net/ppp/ppp_async.c:666
 ppp_async_send+0xe5/0x120 drivers/net/ppp/ppp_async.c:634
 __ppp_channel_push+0xe5/0x230 drivers/net/ppp/ppp_generic.c:2150
 ppp_channel_push+0x1c2/0x250 drivers/net/ppp/ppp_generic.c:2177
 ppp_write+0x236/0x2e0 drivers/net/ppp/ppp_generic.c:525
 do_loop_readv_writev fs/read_write.c:764 [inline]
 do_loop_readv_writev fs/read_write.c:749 [inline]
 vfs_writev+0x6ec/0xde0 fs/read_write.c:973
 do_pwritev+0x1b2/0x260 fs/read_write.c:1072
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7329579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f5f1b5ac EFLAGS: 00000292 ORIG_RAX: 000000000000014e
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000020000380
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	10 06                	adc    %al,(%rsi)
   2:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
   6:	10 07                	adc    %al,(%rdi)
   8:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
   c:	10 08                	adc    %cl,(%rax)
   e:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
  1e:	00 51 52             	add    %dl,0x52(%rcx)
  21:	55                   	push   %rbp
  22:	89 e5                	mov    %esp,%ebp
  24:	0f 34                	sysenter
  26:	cd 80                	int    $0x80
* 28:	5d                   	pop    %rbp <-- trapping instruction
  29:	5a                   	pop    %rdx
  2a:	59                   	pop    %rcx
  2b:	c3                   	ret
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	90                   	nop
  2f:	90                   	nop
  30:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi