linux-kernel - Re: [PATCH] tools: bpftool: close va_list 'ap' by va

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Date:   Mon, 5 Jul 2021 22:58:53 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     gushengxian <gushengxian507419@...il.com>, ast@...nel.org,
        andrii@...nel.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, gushengxian <gushengxian@...ong.com>
Subject: Re: [PATCH] tools: bpftool: close va_list 'ap' by va_end()

On 7/1/21 2:00 PM, gushengxian wrote:
> From: gushengxian <gushengxian@...ong.com>
> 
> va_list 'ap' was opened but not closed by va_end(). It should be
> closed by va_end() before return.
> 
> Signed-off-by: gushengxian <gushengxian@...ong.com>

nit: 'From:' and 'SoB:' should be in standardized form, I presume in your case
this would be:

Gu Shengxian <gushengxian@...ong.com>

> ---
>   tools/bpf/bpftool/jit_disasm.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c
> index e7e7eee9f172..3c85fd1f00cb 100644
> --- a/tools/bpf/bpftool/jit_disasm.c
> +++ b/tools/bpf/bpftool/jit_disasm.c
> @@ -45,8 +45,10 @@ static int fprintf_json(void *out, const char *fmt, ...)
>   	char *s;
>   
>   	va_start(ap, fmt);
> -	if (vasprintf(&s, fmt, ap) < 0)
> +	if (vasprintf(&s, fmt, ap) < 0) {
> +		va_end(ap);
>   		return -1;
> +	}
>   	va_end(ap);

Small nit, please change into something like:

         va_list ap;
         char *s;
+       int err;

         va_start(ap, fmt);
-       if (vasprintf(&s, fmt, ap) < 0)
-               return -1;
+       err = vasprintf(&s, fmt, ap);
         va_end(ap);
+       if (err < 0)
+               return -1;

         if (!oper_count) {
                 int i;

Fwiw, man page says: "On some systems, va_end contains a closing '}' matching a '{' in
va_start, so that both macros must occur in the same function, and in a way that allows
this.".

Thanks,
Daniel