Re: [PATCH v4 bpf-next 1/2] bpf: Fix uninitialized symbol in bpf_perf_link_fill_kprobe()

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, Aug 04, 2023 at 10:57:31AM +0000, Yafang Shao wrote:
> The patch 1b715e1b0ec5: "bpf: Support ->fill_link_info for
> perf_event" from Jul 9, 2023, leads to the following Smatch static
> checker warning:
> 
>     kernel/bpf/syscall.c:3416 bpf_perf_link_fill_kprobe()
>     error: uninitialized symbol 'type'.
> 
> That can happens when uname is NULL. So fix it by verifying the uname
> when we really need to fill it.
> 
> Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event")
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/bpf/85697a7e-f897-4f74-8b43-82721bebc462@kili.mountain/
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Acked-by: Yonghong Song <yonghong.song@linux.dev>

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  kernel/bpf/syscall.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 7f4e8c3..166390f 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3378,14 +3378,14 @@ static int bpf_perf_link_fill_common(const struct perf_event *event,
>  
>  	if (!ulen ^ !uname)
>  		return -EINVAL;
> -	if (!uname)
> -		return 0;
>  
>  	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
>  				      probe_offset, probe_addr);
>  	if (err)
>  		return err;
>  
> +	if (!uname)
> +		return 0;
>  	if (buf) {
>  		len = strlen(buf);
>  		err = bpf_copy_to_user(uname, buf, ulen, len);
> -- 
> 1.8.3.1
>