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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 19 Nov 2018 20:42:26 -0800
Message-ID: <CACT4Y+b1Eq1eXcHJR4tVyn1746pBCNqie8yapuqM3+ry3wJX4g@mail.gmail.com>
Subject: Re: KASAN: use-after-free Read in tick_sched_handle (3)
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     syzbot <syzbot+999bca54de2ee169c021@syzkaller.appspotmail.com>,
        =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= <fweisbec@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        syzkaller-bugs@googlegroups.com,
        Thomas Gleixner <tglx@linutronix.de>,
        netdev <netdev@vger.kernel.org>
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On Mon, Nov 19, 2018 at 8:10 PM, Frederic Weisbecker
<frederic@kernel.org> wrote:
> On Mon, Nov 19, 2018 at 01:39:02PM -0800, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    bae4e109837b mlxsw: spectrum: Expose discard counters via ..
>> git tree:       net-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=11b5e77b400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
>> dashboard link: https://syzkaller.appspot.com/bug?extid=999bca54de2ee169c021
>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14b7d093400000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1487a225400000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+999bca54de2ee169c021@syzkaller.appspotmail.com
>>
>> IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
>> IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
>> 8021q: adding VLAN 0 to HW filter on device team0
>> ==================================================================
>> kasan: CONFIG_KASAN_INLINE enabled
>> BUG: KASAN: use-after-free in tick_sched_handle+0x16c/0x180
>> kernel/time/tick-sched.c:164
>
> So tick_sched_timer() -> tick_sched_handle() is passed regs returned by
> get_irq_regs() that seem to be junk.
>
> Those regs should come from smp_apic_timer_interrupt().
>
> Thoughts?


Looking at the reproducer it looks like some memory corruption in
networking stack. +netdev