netdev - Re: [PATCH iproute2] Fix segv on "-r" option if unknown rpc service

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Message-ID: <20220922120105.7a200fd2@hermes.local>
Date:   Thu, 22 Sep 2022 12:01:05 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] Fix segv on "-r" option if unknown rpc service

On Sun, 18 Sep 2022 02:50:54 +0900
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> wrote:

> +		} else {
> +			const char fmt[] = "%s%u";
> +			char *buf = NULL;
> +			int len = snprintf(buf, 0, fmt, prog,
> +					   rhead->rpcb_map.r_prog);
> +			len++;
> +			buf = malloc(len);
> +			snprintf(buf, len, fmt, prog, rhead->rpcb_map.r_prog);
> +			c->name = buf;
>  		}

Thanks for finding the bug but this could be improved.
This seems like the hard way to do this.
You are reinventing asprintf().

Would this work instead.

diff --git a/misc/ss.c b/misc/ss.c
index ff985cd8cae9..9d3d0bd84df3 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -1596,6 +1596,10 @@ static void init_service_resolver(void)
                if (rpc) {
                        strncat(prog, rpc->r_name, 128 - strlen(prog));
                        c->name = strdup(prog);
+               } else if (asprintf(&c->name, "%s%u",
+                                   prog, rhead->rpcb_map.r_prog) < 0) {
+                       fprintf(stderr, "ss: asprintf failed to allocate buffer\n");
+                       abort();
                }
 
                c->next = rlist;