Re: WARNING: kmalloc bug in xdp_umem_create

[Tetsuo Handa]

On 2018/06/10 20:52, Dmitry Vyukov wrote:
> On Sun, Jun 10, 2018 at 11:31 AM, BjÃrn TÃpel <bjorn.topel@xxxxxxxxx> wrote:
>> Den sÃn 10 juni 2018 kl 04:53 skrev Tetsuo Handa
>> <penguin-kernel@xxxxxxxxxxxxxxxxxxx>:
>>>
>>> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
>>>>
>>>> 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.