Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in tty_ldisc_receive_buf

[syzbot <syzbot+be4b95faeb7a9073bb88@syzkaller.appspotmail.com>]

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

can't find the dup bug

> 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@syzkaller.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@googlegroups.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
>
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