linux-kernel - Re: [PATCH] bpf: fix kmalloc bug in bpf

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Date:   Mon, 13 Sep 2021 23:36:13 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Willy Tarreau <w@....eu>,
        syzbot+f3e749d4c662818ae439@...kaller.appspotmail.com,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        bpf@...r.kernel.org, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: fix kmalloc bug in bpf_check

On Mon, Sep 13, 2021 at 11:34 PM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 9/13/21 4:02 AM, Dongliang Mu wrote:
> > Since 7661809d493b ("mm: don't allow oversized kvmalloc() calls
> > ") does not allow oversized kvmalloc, it triggers a kmalloc bug warning
> > at bpf_check.
> >
> > Fix it by adding a sanity check in th check_btf_line.
> >
> > Reported-by: syzbot+f3e749d4c662818ae439@...kaller.appspotmail.com
> > Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls")
> > Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
>
> Thanks for the fix. A similar patch has been proposed here:
> https://lore.kernel.org/bpf/20210911005557.45518-1-cuibixuan@huawei.com/

OK, I see. Let's ignore this patch.

>
> > ---
> >   kernel/bpf/verifier.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 047ac4b4703b..3c5a79f78bc5 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -9913,6 +9913,9 @@ static int check_btf_line(struct bpf_verifier_env *env,
> >       if (!nr_linfo)
> >               return 0;
> >
> > +     if (nr_linfo > INT_MAX/sizeof(struct bpf_line_info))
> > +             return -EINVAL;
> > +
> >       rec_size = attr->line_info_rec_size;
> >       if (rec_size < MIN_BPF_LINEINFO_SIZE ||
> >           rec_size > MAX_LINEINFO_REC_SIZE ||
> >