linux-kernel - Re: WARNING in kvmalloc

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Date:   Wed, 14 Feb 2018 19:47:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        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, "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: WARNING in kvmalloc_node



On 2018年02月14日 17:28, Daniel Borkmann wrote:
> [ +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!

It looks to me the only solution is to revert that commit.

Will post a patch.

Thanks