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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sun, 10 Jun 2018 14:58:33 +0200
Message-ID: <CACT4Y+Y6TDof6vvdQYHF_W8aAgHPuW_DS2A9HCudmYx549u0Ag@mail.gmail.com>
Subject: Re: WARNING: kmalloc bug in xdp_umem_create
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>,
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        "Karlsson, Magnus" <magnus.karlsson@intel.com>,
        David Miller <davem@davemloft.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
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On Sun, Jun 10, 2018 at 2:53 PM, Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
> On 2018/06/10 20:52, Dmitry Vyukov wrote:
>> On Sun, Jun 10, 2018 at 11:31 AM, Bj=C3=B6rn T=C3=B6pel <bjorn.topel@gma=
il.com> wrote:
>>> Den s=C3=B6n 10 juni 2018 kl 04:53 skrev Tetsuo Handa
>>> <penguin-kernel@i-love.sakura.ne.jp>:
>>>>
>>>> On 2018/06/10 7:47, syzbot wrote:
>>>>> Hello,
>>>>>
>>>>> syzbot found the following crash on:
>>>>>
>>>>> HEAD commit:    7d3bf613e99a Merge tag 'libnvdimm-for-4.18' of git://=
git.k..
>>>>> git tree:       upstream
>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D1073f68f8=
00000
>>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=3Df04d8d0a2=
afb789a
>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=3D4abadc5d691=
17b346506
>>>>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>>>>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=3D13c9756=
f800000
>>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D16366f9f8=
00000
>>>>>
>>>>> IMPORTANT: if you fix the bug, please add the following tag to the co=
mmit:
>>>>> Reported-by: syzbot+4abadc5d69117b346506@syzkaller.appspotmail.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)
>>>>> random: sshd: uninitialized urandom read (32 bytes read)
>>>>> random: sshd: uninitialized urandom read (32 bytes read)
>>>>> WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0=
x70 mm/slab_common.c:996
>>>>> Kernel panic - not syncing: panic_on_warn set ...
>>>>
>>>> syzbot gave up upon kmalloc(), but actually error handling path has
>>>> NULL pointer dereference bug.
>>>>
>>>
>>> Thanks Tetsuo! This crash has been fixed by Daniel Borkmann in commit
>>> c09290c56376 ("bpf, xdp: fix crash in xdp_umem_unaccount_pages").
>>
>> Let's tell syzbot about this:
>>
>> #syz fix: bpf, xdp: fix crash in xdp_umem_unaccount_pages
>>
>>
> Excuse me, but that patch fixes NULL pointer dereference which occurs aft=
er kmalloc()'s
> "WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70=
 mm/slab_common.c:996"
> message. That is, "Too large memory allocation" itself is not yet fixed.

You are right! I fixed it up. Thanks