netdev - Re: WARNING in pcpu

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Message-ID: <CAADnVQ+DyZ5ze4gjfgQz+OATRE_Jd1b5D1osq8+8O3BL9vHzhg@mail.gmail.com>
Date:   Mon, 1 Oct 2018 18:23:43 +0000
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     syzbot+18628320d3b14a5c459c@...kaller.appspotmail.com,
        Roman Gushchin <guro@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: WARNING in pcpu_alloc

On Mon, Oct 1, 2018 at 6:14 PM syzbot
<syzbot+18628320d3b14a5c459c@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    c5a9f9817ba5 Merge branch 'bpf-per-cpu-cgroup-local-storage'
> git tree:       bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=175f98e6400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=443816db871edd66
> dashboard link: https://syzkaller.appspot.com/bug?extid=18628320d3b14a5c459c
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=129cbd1a400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16685ac9400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+18628320d3b14a5c459c@...kaller.appspotmail.com
>
> ------------[ cut here ]------------
> illegal size (0) or align (8) for percpu allocation

Roman,

looks like
        if (attr->value_size > PAGE_SIZE)
                return ERR_PTR(-E2BIG);
is not enough, since value_size==0 needs to be rejected as well.
Could you prepare a patch?