Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: WARNING: kmalloc bug in xdp_umem_create
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>,
        syzbot+4abadc5d69117b346506@syzkaller.appspotmail.com,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        "Karlsson, Magnus" <magnus.karlsson@intel.com>,
        David Miller <davem@davemloft.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
References: <00000000000092de58056e3d4b96@google.com>
 <10d6b170-b820-3077-8737-c9d06e98d0fb@I-love.SAKURA.ne.jp>
 <CAJ+HfNhnmvTHsE7cgi8pROjprsYvCZuzZDmYmpiUx4jqtHboUw@mail.gmail.com>
 <CACT4Y+bfZK6yucoDrXPPW3Tc40RYq61u0Zcb=CKtdao8E+v1cQ@mail.gmail.com>
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <13f6777a-2170-d0cc-1066-1b48a27ec981@i-love.sakura.ne.jp>
Date:   Sun, 10 Jun 2018 21:53:07 +0900
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.8.0
MIME-Version: 1.0
In-Reply-To: <CACT4Y+bfZK6yucoDrXPPW3Tc40RYq61u0Zcb=CKtdao8E+v1cQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2018/06/10 20:52, Dmitry Vyukov wrote:
> On Sun, Jun 10, 2018 at 11:31 AM, Björn Töpel <bjorn.topel@gmail.com> wrote:
>> Den sön 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=1073f68f800000
>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=f04d8d0a2afb789a
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=4abadc5d69117b346506
>>>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>>>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13c9756f800000
>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16366f9f800000
>>>>
>>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>>> 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+0x56/0x70 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 after 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.