From e01c92a5ef6127067922f74cd8dac2ba72a1ad52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?George=20Anderson=20Guimar=C3=A3es?=
 <571682+georgeanderson@users.noreply.github.com>
Date: Tue, 11 May 2021 06:27:08 -0500
Subject: [PATCH] improve error handing in anetFDToString to avoid returning
 successfully with garbage. (#8678)

Check for errors in inet_ntop and snprintf rather than ignore them
and return success (with garbage output).
The check for ip_len == 0 seems like dead code, removed.
---
 src/anet.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/anet.c b/src/anet.c
index 04ccc540d..381dda375 100644
--- a/src/anet.c
+++ b/src/anet.c
@@ -541,18 +541,26 @@ int anetFdToString(int fd, char *ip, size_t ip_len, int *port, int fd_to_str_typ
     } else {
         if (getsockname(fd, (struct sockaddr *)&sa, &salen) == -1) goto error;
     }
-    if (ip_len == 0) goto error;
 
     if (sa.ss_family == AF_INET) {
         struct sockaddr_in *s = (struct sockaddr_in *)&sa;
-        if (ip) inet_ntop(AF_INET,(void*)&(s->sin_addr),ip,ip_len);
+        if (ip) {
+            if (inet_ntop(AF_INET,(void*)&(s->sin_addr),ip,ip_len) == NULL)
+                goto error;
+        }
         if (port) *port = ntohs(s->sin_port);
     } else if (sa.ss_family == AF_INET6) {
         struct sockaddr_in6 *s = (struct sockaddr_in6 *)&sa;
-        if (ip) inet_ntop(AF_INET6,(void*)&(s->sin6_addr),ip,ip_len);
+        if (ip) {
+            if (inet_ntop(AF_INET6,(void*)&(s->sin6_addr),ip,ip_len) == NULL)
+                goto error;
+        }
         if (port) *port = ntohs(s->sin6_port);
     } else if (sa.ss_family == AF_UNIX) {
-        if (ip) snprintf(ip, ip_len, "/unixsocket");
+        if (ip) {
+            int res = snprintf(ip, ip_len, "/unixsocket");
+            if (res < 0 || (unsigned int) res >= ip_len) goto error;
+        }
         if (port) *port = 0;
     } else {
         goto error;