linux-kernel - Re: KASAN: stack-out-of-bounds Read in timerqueue

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Message-ID: <CACT4Y+b0fysS3D4QCcfw5X-rFt3c1a7XAHntN4Q7p9tdHNCuow@mail.gmail.com>
Date:   Wed, 4 Jul 2018 18:34:52 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+b680e42077a0d7c9a0c4@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: KASAN: stack-out-of-bounds Read in timerqueue_add

On Wed, Jul 4, 2018 at 6:29 PM, syzbot
<syzbot+b680e42077a0d7c9a0c4@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    fc36def997cf mm: teach dump_page() to correctly output poi..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=167e3b92400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f62553dc846b0692
> dashboard link: https://syzkaller.appspot.com/bug?extid=b680e42077a0d7c9a0c4
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1030a858400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1167aaa4400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b680e42077a0d7c9a0c4@...kaller.appspotmail.com

+bpf maintainers since the repro seems to deal to bpf maps

We've got a splash of crashes today, all seem to suggest some kind of
stack corruption/overflow, see the last 6 bugs here:
https://syzkaller.appspot.com/



> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> IPVS: ftp: loaded support on port[0] = 21
> ==================================================================
> BUG: KASAN: stack-out-of-bounds in timerqueue_add+0x249/0x2b0
> lib/timerqueue.c:52
> Read of size 8 at addr ffff8801af537cf8 by task syz-executor591/7178
>
> CPU: 0 PID: 7178 Comm: syz-executor591 Not tainted 4.18.0-rc3+ #130
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  timerqueue_add+0x249/0x2b0 lib/timerqueue.c:52
>  enqueue_hrtimer+0x18e/0x540 kernel/time/hrtimer.c:960
>  __run_hrtimer kernel/time/hrtimer.c:1413 [inline]
>  __hrtimer_run_queues+0xc07/0x10c0 kernel/time/hrtimer.c:1460
>  hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
>  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
>  smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050
>  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
>  </IRQ>
>
> The buggy address belongs to the page:
> page:ffffea0006bd4dc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
> flags: 0x2fffc0000000000()
> raw: 02fffc0000000000 0000000000000000 ffffffff06bd0101 0000000000000000
> raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801af537b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff8801af537c00: 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 f2 f2 f2 f2
>>
>> ffff8801af537c80: 00 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2 f2 f2
>
>                                                                 ^
>  ffff8801af537d00: f8 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 00 00 00 00
>  ffff8801af537d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================
>
>
> ---
> This bug 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 bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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