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gh-159739: Account for NUL terminators in fallback getnameinfo #159991

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Merged
JelleZijlstra merged 1 commit into from
Oct 21, 2026
+7 −5
Merged

gh-159739: Account for NUL terminators in fallback getnameinfo #159991

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-10-20-00-00-00.gh-issue-159739.1e4599.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix off-by-one output buffer checks in the fallback implementation of
``getnameinfo()``.
10 changes: 5 additions & 5 deletions Modules/getnameinfo.c
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Original file line number Diff line number Diff line change
Expand Up @@ -130,13 +130,13 @@ getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen,
/* what we should do? */
} else if (flags & NI_NUMERICSERV) {
sprintf(numserv, "%d", ntohs(port));
if (strlen(numserv) > servlen)
if (strlen(numserv) >= servlen)
return ENI_MEMORY;
strcpy(serv, numserv);
} else {
sp = getservbyport(port, (flags & NI_DGRAM) ? "udp" : "tcp");
if (sp) {
if (strlen(sp->s_name) > servlen)
if (strlen(sp->s_name) >= servlen)
return ENI_MEMORY;
strcpy(serv, sp->s_name);
} else
Expand Down Expand Up @@ -166,7 +166,7 @@ getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen,
if (inet_ntop(gni_afd->a_af, addr, numaddr, sizeof(numaddr))
== NULL)
return ENI_SYSTEM;
if (strlen(numaddr) > hostlen)
if (strlen(numaddr) >= hostlen)
return ENI_MEMORY;
strcpy(host, numaddr);
} else {
Expand All @@ -181,7 +181,7 @@ getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen,
p = strchr(hp->h_name, '.');
if (p) *p = '\0';
}
if (strlen(hp->h_name) > hostlen) {
if (strlen(hp->h_name) >= hostlen) {
#ifdef ENABLE_IPV6
freehostent(hp);
#endif
Expand All @@ -197,7 +197,7 @@ getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen,
if (inet_ntop(gni_afd->a_af, addr, numaddr, sizeof(numaddr))
== NULL)
return ENI_NOHOSTNAME;
if (strlen(numaddr) > hostlen)
if (strlen(numaddr) >= hostlen)
return ENI_MEMORY;
strcpy(host, numaddr);
}
Expand Down
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