Re: [iproute PATCH v2 4/7] lib/inet_proto: Make sure destination buffers are NULL-terminated

On Fri, Aug 18, 2017 at 09:37:33AM -0700, Stephen Hemminger wrote:

On Thu, 17 Aug 2017 19:09:29 +0200
Phil Sutter [off-list ref] wrote:

quoted

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 lib/inet_proto.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/inet_proto.c b/lib/inet_proto.c
index ceda082b12a2e..87ed4769fc3da 100644
--- a/lib/inet_proto.c
+++ b/lib/inet_proto.c

@@ -35,8 +35,10 @@ const char *inet_proto_n2a(int proto, char *buf, int len)
 	pe = getprotobynumber(proto);
 	if (pe) {
 		icache = proto;
-		strncpy(ncache, pe->p_name, 16);
-		strncpy(buf, pe->p_name, len);
+		strncpy(ncache, pe->p_name, 15);
+		ncache[15] = '\0';
+		strncpy(buf, pe->p_name, len - 1);
+		buf[len] = '\0';
 		return buf;
 	}
 	snprintf(buf, len, "ipproto-%d", proto);

@@ -62,7 +64,8 @@ int inet_proto_a2n(const char *buf)
 	pe = getprotobyname(buf);
 	if (pe) {
 		icache = pe->p_proto;
-		strncpy(ncache, pe->p_name, 16);
+		strncpy(ncache, pe->p_name, 15);
+		ncache[15] = '\0';
 		return pe->p_proto;
 	}
 	return -1;

Depending on proto name to be 15 characters or less is a silly
choice. Why not use strdup() and do it right?

Yes, I was puzzled by that as well. Luckily the longest proto name in my
/etc/protocols is rsvp-e2e-ignore which is 15 chars long. I'll change
the patch to use dynamic allocation.

Thanks, Phil