Re: general protection fault in n_tty_receive_buf_common

[Dmitry Vyukov]

On Fri, Oct 27, 2017 at 11:22 AM, syzbot
<bot+7fde9fa6e982d17b9acf978961e059b0a5344719@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> 623ce3456671ea842c0ebda79c38655c8c04af74
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.

A more recent report is on upstream 0787643a5f6aad1f0cdeb305f7fe492b71943ea4

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 59 Comm: kworker/u4:2 Not tainted 4.14.0-rc5+ #142
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
task: ffff8801d9aa6700 task.stack: ffff8801d9ab0000
RIP: 0010:__read_once_size include/linux/compiler.h:276 [inline]
RIP: 0010:n_tty_receive_buf_common+0x154/0x2520 drivers/tty/n_tty.c:1690
RSP: 0018:ffff8801d9ab7130 EFLAGS: 00010202
RAX: 000000000000044c RBX: ffff8801d4cb0400 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8801d4cb07a8 RDI: 0000000000002260
RBP: ffff8801d9ab72d8 R08: ffffffff82721563 R09: 0000000000000005
R10: ffff8801d9ab6f68 R11: 0000000000000002 R12: ffff8801d28ed27f
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff8801d28ed27f
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f97bb6e6330 CR3: 00000001c5959000 CR4: 00000000001426e0
Call Trace:
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 tty_ldisc_receive_buf+0xa7/0x180 drivers/tty/tty_buffer.c:455
 tty_port_default_receive_buf+0x106/0x160 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:474 [inline]
 flush_to_ldisc+0x3c4/0x590 drivers/tty/tty_buffer.c:523
 process_one_work+0xbf0/0x1bc0 kernel/workqueue.c:2119
 worker_thread+0x223/0x1860 kernel/workqueue.c:2253
 kthread+0x35e/0x430 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
Code: 89 85 18 ff ff ff 48 8d 45 98 48 89 85 e0 fe ff ff e8 61 a8 fb
fe 48 8b 85 18 ff ff ff c6 00 00 48 8b 85 a0 fe ff ff 48 c1 e8 03 <42>
80 3c 30 00 0f 85 6d 1e 00 00 48 8b 85 28 ff ff ff 4c 8b a8
RIP: __read_once_size include/linux/compiler.h:276 [inline] RSP:
ffff8801d9ab7130
RIP: n_tty_receive_buf_common+0x154/0x2520 drivers/tty/n_tty.c:1690
RSP: ffff8801d9ab7130
---[ end trace b62a8a78df2eb9d9 ]---


> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
> SELinux: unrecognized netlink message: protocol=4 nlmsg_type=32
> sclass=netlink_tcpdiag_socket pig=18822 comm=syz-executor4
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3797 Comm: kworker/u4:5 Not tainted 4.13.0-rc4+ #24
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: events_unbound flush_to_ldisc
> task: ffff8801c6abc340 task.stack: ffff8801c6a08000
> RIP: 0010:__read_once_size include/linux/compiler.h:250 [inline]
> RIP: 0010:n_tty_receive_buf_common+0x154/0x2520 drivers/tty/n_tty.c:1690
> RSP: 0018:ffff8801c6a0f130 EFLAGS: 00010202
> RAX: 000000000000044c RBX: ffff8801c8c0f680 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff8801c8c0fa28 RDI: 0000000000002260
> RBP: ffff8801c6a0f2d8 R08: 0000000000000004 R09: 0000000000000005
> R10: ffff8801c6a0ef68 R11: ffffffff8266dad3 R12: ffff8801c73d5b82
> R13: ffff8801c73d5c82 R14: dffffc0000000000 R15: ffff8801c73d5b82
> SELinux: unrecognized netlink message: protocol=4 nlmsg_type=32
> sclass=netlink_tcpdiag_socket pig=18822 comm=syz-executor4
> FS:  0000000000000000(0000) GS:ffff8801dc000000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000000 CR3: 0000000005021000 CR4: 00000000001406f0
> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> Call Trace:
>  n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
>  tty_ldisc_receive_buf+0xa7/0x180 drivers/tty/tty_buffer.c:429
>  tty_port_default_receive_buf+0x106/0x160 drivers/tty/tty_port.c:37
>  receive_buf drivers/tty/tty_buffer.c:448 [inline]
>  flush_to_ldisc+0x3c4/0x590 drivers/tty/tty_buffer.c:497
>  process_one_work+0xbf3/0x1bc0 kernel/workqueue.c:2097
>  worker_thread+0x223/0x1860 kernel/workqueue.c:2231
>  kthread+0x35e/0x430 kernel/kthread.c:231
>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425
> Code: 89 85 18 ff ff ff 48 8d 45 98 48 89 85 e0 fe ff ff e8 71 cb 06 ff 48
> 8b 85 18 ff ff ff c6 00 00 48 8b 85 a0 fe ff ff 48 c1 e8 03 <42> 80 3c 30 00
> 0f 85 6d 1e 00 00 48 8b 85 28 ff ff ff 4c 8b a8
> RIP: __read_once_size include/linux/compiler.h:250 [inline] RSP:
> ffff8801c6a0f130
> RIP: n_tty_receive_buf_common+0x154/0x2520 drivers/tty/n_tty.c:1690 RSP:
> ffff8801c6a0f130
> ---[ end trace 1e2f55861d14ef37 ]---
> Kernel panic - not syncing: Fatal exception
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
>
>
> ---
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> See https://goo.gl/tpsmEJ for details.
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