linux-kernel - Re: WARNING in kvmalloc

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Date:   Wed, 14 Feb 2018 10:28:26 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Cc:     syzbot <syzbot+1a240cdb1f4cc88819df@...kaller.appspotmail.com>,
        akpm@...ux-foundation.org, dhowells@...hat.com, hannes@...xchg.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mingo@...nel.org,
        rppt@...ux.vnet.ibm.com, syzkaller-bugs@...glegroups.com,
        vbabka@...e.cz, viro@...iv.linux.org.uk,
        Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org,
        brouer@...hat.com, jasowang@...hat.com
Subject: Re: WARNING in kvmalloc_node

[ +Jason, +Jesper ]

On 02/14/2018 09:43 AM, Michal Hocko wrote:
> On Tue 13-02-18 18:55:33, Matthew Wilcox wrote:
>> On Tue, Feb 13, 2018 at 03:59:01PM -0800, syzbot wrote:
> [...]
>>>  kvmalloc include/linux/mm.h:541 [inline]
>>>  kvmalloc_array include/linux/mm.h:557 [inline]
>>>  __ptr_ring_init_queue_alloc include/linux/ptr_ring.h:474 [inline]
>>>  ptr_ring_init include/linux/ptr_ring.h:492 [inline]
>>>  __cpu_map_entry_alloc kernel/bpf/cpumap.c:359 [inline]
>>>  cpu_map_update_elem+0x3c3/0x8e0 kernel/bpf/cpumap.c:490
>>>  map_update_elem kernel/bpf/syscall.c:698 [inline]
>>
>> Blame the BPF people, not the MM people ;-)

Heh, not really. ;-)

> Yes. kvmalloc (the vmalloc part) doesn't support GFP_ATOMIC semantic.

Agree, that doesn't work.

Bug was added in commit 0bf7800f1799 ("ptr_ring: try vmalloc() when kmalloc() fails").

Jason, please take a look at fixing this, thanks!