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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Tue, 14 Jul 2020 10:27:42 -0700
Message-ID: <CAADnVQ+jUPGJapkvKW=AfXESD6Vz2iuONvJm8eJm5Yd+u9mJ+w@mail.gmail.com>
Subject: Re: [Linux-kernel-mentees] [PATCH v2] bpf: Fix NULL pointer
 dereference in __btf_resolve_helper_id()
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Peilin Ye <yepeilin.cs@gmail.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        open list <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Mon, Jul 13, 2020 at 9:38 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Jul 13, 2020 at 6:29 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >
> > Prevent __btf_resolve_helper_id() from dereferencing `btf_vmlinux`
> > as NULL. This patch fixes the following syzbot bug:
> >
> >     https://syzkaller.appspot.com/bug?id=5edd146856fd513747c1992442732e5a0e9ba355

The link looks wrong?
Nothing in the stack trace indicates this issue.

> > Reported-by: syzbot+ee09bda7017345f1fbe6@syzkaller.appspotmail.com
> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> > ---
> > Thank you for reviewing my patch! I am new to Linux kernel development; would
> > the log message and errno be appropriate for this case?
>
> I think it's good enough, thanks for the fix.
>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
>
> >
> > Change in v2:
> >     - Split NULL and IS_ERR cases.
> >
> >  kernel/bpf/btf.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
>
> [...]