netdev - Re: [PATCH] samples: bpf: fix: seg fault with NULL pointer arg

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Message-ID: <CAPhsuW4Xm+RYftacCYEhfKHDT57jqK=ssV7GWCoNvRp=6YH-0A@mail.gmail.com>
Date:   Sun, 2 Dec 2018 23:52:29 -0800
From:   Song Liu <liu.song.a23@...il.com>
To:     danieltimlee@...il.com
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH] samples: bpf: fix: seg fault with NULL pointer arg

On Sat, Dec 1, 2018 at 1:07 PM Daniel T. Lee <danieltimlee@...il.com> wrote:
>
> When NULL pointer accidentally passed to write_kprobe_events,
> due to strlen(NULL), segmentation fault happens.
> Changed code returns -1 to deal with this situation.
>
> Bug issued with Smatch, static analysis.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> ---
>  samples/bpf/bpf_load.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
> index 434ea34a5954..c670bd2200d2 100644
> --- a/samples/bpf/bpf_load.c
> +++ b/samples/bpf/bpf_load.c
> @@ -58,7 +58,9 @@ static int write_kprobe_events(const char *val)
>  {
>         int fd, ret, flags;
>
> -       if ((val != NULL) && (val[0] == '\0'))
> +       if (val == NULL)
> +               return -1;
> +       else if ((val != NULL) && (val[0] == '\0'))

We only need
+       else if (val[0] == '\0')
right?

Thanks,
Song