nss-resolve: report ERANGE for small buffers. (#5359)

The correct error code to report when a provided buffer is too small is
ERANGE. This is recognized by glibc, which will then try again with a
larger buffer. The old behaviour of reporting ENOMEM has no special
meaning for glibc. The error will simply be propagated to the
application, and a later retry will trigger the same error again.

Additionally, h_errnop must be set to NETDB_INTERNAL to have glibc look
at errnop for details.

More information at:
https://www.gnu.org/software/libc/manual/html_node/NSS-Modules-Interface.html

diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index ce8d59d..440dd4b 100644 (file)
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -206,8 +206,8 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         l = strlen(canonical);
         ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * c;
         if (buflen < ms) {
-                *errnop = ENOMEM;
-                *h_errnop = TRY_AGAIN;
+                *errnop = ERANGE;
+                *h_errnop = NETDB_INTERNAL;
                 return NSS_STATUS_TRYAGAIN;
         }
 
@@ -394,8 +394,8 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         ms = ALIGN(l+1) + c * ALIGN(alen) + (c+2) * sizeof(char*);
 
         if (buflen < ms) {
-                *errnop = ENOMEM;
-                *h_errnop = TRY_AGAIN;
+                *errnop = ERANGE;
+                *h_errnop = NETDB_INTERNAL;
                 return NSS_STATUS_TRYAGAIN;
         }
 
@@ -615,8 +615,8 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
               c * sizeof(char*);        /* pointers to aliases, plus trailing NULL */
 
         if (buflen < ms) {
-                *errnop = ENOMEM;
-                *h_errnop = TRY_AGAIN;
+                *errnop = ERANGE;
+                *h_errnop = NETDB_INTERNAL;
                 return NSS_STATUS_TRYAGAIN;
         }