linux-kernel - Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in tty_ldisc_receive

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Date:   Mon, 29 Aug 2022 10:40:32 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     syzbot <syzbot+be4b95faeb7a9073bb88@...kaller.appspotmail.com>,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in
 tty_ldisc_receive_buf

#syz dup: BUG: unable to handle kernel NULL pointer dereference in 
gsmld_receive_buf

On 24. 08. 22, 18:35, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    1c23f9e627a7 Linux 6.0-rc2
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=177ac367080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3045c937aad027f7
> dashboard link: https://syzkaller.appspot.com/bug?extid=be4b95faeb7a9073bb88
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1701758d080000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17473aad080000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+be4b95faeb7a9073bb88@...kaller.appspotmail.com
> 
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> Mem abort info:
>    ESR = 0x0000000086000006
>    EC = 0x21: IABT (current EL), IL = 32 bits
>    SET = 0, FnV = 0
>    EA = 0, S1PTW = 0
>    FSC = 0x06: level 2 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=000000010b44f000
> [0000000000000000] pgd=080000010b5f3003, p4d=080000010b5f3003, pud=080000010b1ce003, pmd=0000000000000000
> Internal error: Oops: 86000006 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 1 PID: 28 Comm: kworker/u4:1 Not tainted 6.0.0-rc2-syzkaller-16440-g1c23f9e627a7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/20/2022
> Workqueue: events_unbound flush_to_ldisc
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : gsmld_receive_buf+0x140/0x214 drivers/tty/n_gsm.c:2861
> sp : ffff80000f603c30
> x29: ffff80000f603c40 x28: 0000000000000000 x27: 00000000000003d9
> x26: 0000000000000000 x25: 0000000000000000 x24: ffff80000d937000
> x23: ffff80000d681e40 x22: ffff0000c929b800 x21: 0000000000000000
> x20: ffff80000c205988 x19: ffff0000c91cf446 x18: ffff80000d2dec40
> x17: 0000000000000008 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000004 x12: ffff80000d681e78
> x11: ff808000098e7e04 x10: 0000000000000000 x9 : ffff8000098e7e04
> x8 : 0000000000000000 x7 : ffff8000098dac3c x6 : 0000000000000000
> x5 : 0000000000000000 x4 : 0000000000000001 x3 : 00000000000003da
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c929b800
> Call trace:
>   0x0
>   tty_ldisc_receive_buf+0xb8/0xcc drivers/tty/tty_buffer.c:461
>   tty_port_default_receive_buf+0x54/0x8c drivers/tty/tty_port.c:39
>   receive_buf drivers/tty/tty_buffer.c:511 [inline]
>   flush_to_ldisc+0x150/0x358 drivers/tty/tty_buffer.c:561
>   process_one_work+0x2d8/0x504 kernel/workqueue.c:2289
>   worker_thread+0x340/0x610 kernel/workqueue.c:2436
>   kthread+0x12c/0x158 kernel/kthread.c:376
>   ret_from_fork+0x10/0x20
> Code: bad PC value
> ---[ end trace 0000000000000000 ]---
> 
> 
> ---
> 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@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

-- 
js
suse labs