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

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

[OGAWA Hirofumi]

In init_service_resolver(), if getrpcbynumber() returned NULL, c->name
is pointing the undefined memory. So "-r" can segv for example.

So this patch uses "rpc.<r_prog>" format like the following if rpc
name is unresolved, instead of segv or raw port number.

	tcp   LISTEN  0  64  0.0.0.0:rpc.100227  0.0.0.0:*

[Or we would be able to set c->name = NULL to use raw port number]

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
 misc/ss.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/misc/ss.c b/misc/ss.c
index ff985cd..866e278 100644
--- a/misc/ss.c	2022-08-25 16:22:06.454913793 +0900
+++ b/misc/ss.c	2022-09-18 02:48:24.212779850 +0900
@@ -1596,6 +1596,15 @@ static void init_service_resolver(void)
 		if (rpc) {
 			strncat(prog, rpc->r_name, 128 - strlen(prog));
 			c->name = strdup(prog);
+		} 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;
 		}
 
 		c->next = rlist;
_

-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

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

[Stephen Hemminger]

On Sun, 18 Sep 2022 02:50:54 +0900
OGAWA Hirofumi <hirofumi@mail.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;

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

[OGAWA Hirofumi]

Stephen Hemminger <stephen@networkplumber.org> writes:

> On Sun, 18 Sep 2022 02:50:54 +0900
> OGAWA Hirofumi <hirofumi@mail.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().

Right, if this project is assuming the extension is available.

> Would this work instead.

Thanks.

> 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;

-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>