getaddrinfo: Always allocate canonical name on the heap

A further simplification could eliminate the canon variable in
gaih_inet and replace it with canonbuf.  However, canonbuf is
used as a flag in the nscd code, which makes this somewhat
non-straightforward.

diff --git a/ChangeLog b/ChangeLog
index 02a7c41a746780b12f78f0ba4a45b12041f9a554..579258f02a0bfcfc9e2549b202aa786bb1a33d2a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-06-02  Florian Weimer  <fweimer@redhat.com>
+
+       * sysdeps/posix/getaddrinfo.c (getcanonname): New function.
+       (gaih_inet): Remove malloc_canonbuf variable.  Call getcanonname.
+
 2017-06-02  Florian Weimer  <fweimer@redhat.com>
 
        * malloc/Makefile (routines): Add dynarray_at_failure,

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index dc02b11d6e9dcdd9a7246d7f41125be491887cec..d92db7012131eeac609262f0cc712a2aeecc1659 100644 (file)
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -308,6 +308,30 @@ typedef enum nss_status (*nss_getcanonname_r)
    int *errnop, int *h_errnop);
 extern service_user *__nss_hosts_database attribute_hidden;
 
+/* This function is called if a canonical name is requested, but if
+   the service function did not provide it.  It tries to obtain the
+   name using getcanonname_r from the same service NIP.  If the name
+   cannot be canonicalized, return a copy of NAME.  Return NULL on
+   memory allocation failure.  The returned string is allocated on the
+   heap; the caller has to free it.  */
+static char *
+getcanonname (service_user *nip, struct gaih_addrtuple *at, const char *name)
+{
+  nss_getcanonname_r cfct = __nss_lookup_function (nip, "getcanonname_r");
+  char *s = (char *) name;
+  if (cfct != NULL)
+    {
+      char buf[256];
+      int herrno;
+      int rc;
+      if (DL_CALL_FCT (cfct, (at->name ?: name, buf, sizeof (buf),
+                             &s, &rc, &herrno)) != NSS_STATUS_SUCCESS)
+       /* If the canonical name cannot be determined, use the passed
+          string.  */
+       s = (char *) name;
+    }
+  return strdup (name);
+}
 
 static int
 gaih_inet (const char *name, const struct gaih_service *service,
@@ -443,7 +467,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
   bool malloc_name = false;
   struct gaih_addrtuple *addrmem = NULL;
-  bool malloc_canonbuf = false;
   char *canonbuf = NULL;
   int result = 0;
 
@@ -702,22 +725,13 @@ gaih_inet (const char *name, const struct gaih_service *service,
                        (*pat)->name = NULL;
                      else if (canonbuf == NULL)
                        {
-                         size_t canonlen = strlen (air->canon) + 1;
-                         if ((req->ai_flags & AI_CANONIDN) != 0
-                             && __libc_use_alloca (alloca_used + canonlen))
-                           canonbuf = alloca_account (canonlen, alloca_used);
-                         else
+                         canonbuf = strdup (air->canon);
+                         if (canonbuf == NULL)
                            {
-                             canonbuf = malloc (canonlen);
-                             if (canonbuf == NULL)
-                               {
-                                 result = -EAI_MEMORY;
-                                 goto free_and_return;
-                               }
-                             malloc_canonbuf = true;
+                             result = -EAI_MEMORY;
+                             goto free_and_return;
                            }
-                         canon = (*pat)->name = memcpy (canonbuf, air->canon,
-                                                        canonlen);
+                         canon = (*pat)->name = canonbuf;
                        }
 
                      if (air->family[i] == AF_INET
@@ -924,55 +938,16 @@ gaih_inet (const char *name, const struct gaih_service *service,
                          if ((req->ai_flags & AI_CANONNAME) != 0
                              && canon == NULL)
                            {
-                             /* If we need the canonical name, get it
-                                from the same service as the result.  */
-                             nss_getcanonname_r cfct;
-                             int herrno;
-
-                             cfct = __nss_lookup_function (nip,
-                                                           "getcanonname_r");
-                             if (cfct != NULL)
+                             canonbuf = getcanonname (nip, at, name);
+                             if (canonbuf == NULL)
                                {
-                                 const size_t max_fqdn_len = 256;
-                                 if ((req->ai_flags & AI_CANONIDN) != 0
-                                     && __libc_use_alloca (alloca_used
-                                                           + max_fqdn_len))
-                                   canonbuf = alloca_account (max_fqdn_len,
-                                                              alloca_used);
-                                 else
-                                   {
-                                     canonbuf = malloc (max_fqdn_len);
-                                     if (canonbuf == NULL)
-                                       {
-                                         _res.options
-                                           |= old_res_options
-                                              & DEPRECATED_RES_USE_INET6;
-                                         result = -EAI_MEMORY;
-                                         goto free_and_return;
-                                       }
-                                     malloc_canonbuf = true;
-                                   }
-                                 char *s;
-
-                                 if (DL_CALL_FCT (cfct, (at->name ?: name,
-                                                         canonbuf,
-                                                         max_fqdn_len,
-                                                         &s, &rc, &herrno))
-                                     == NSS_STATUS_SUCCESS)
-                                   canon = s;
-                                 else
-                                   {
-                                     /* If the canonical name cannot be
-                                        determined, use the passed in
-                                        string.  */
-                                     if (malloc_canonbuf)
-                                       {
-                                         free (canonbuf);
-                                         malloc_canonbuf = false;
-                                       }
-                                     canon = name;
-                                   }
+                                 _res.options
+                                   |= old_res_options
+                                   & DEPRECATED_RES_USE_INET6;
+                                 result = -EAI_MEMORY;
+                                 goto free_and_return;
                                }
+                             canon = canonbuf;
                            }
                          status = NSS_STATUS_SUCCESS;
                        }
@@ -1118,9 +1093,10 @@ gaih_inet (const char *name, const struct gaih_service *service,
 #ifdef HAVE_LIBIDN
              make_copy:
 #endif
-               if (malloc_canonbuf)
-                 /* We already allocated the string using malloc.  */
-                 malloc_canonbuf = false;
+               if (canonbuf != NULL)
+                 /* We already allocated the string using malloc, but
+                    the buffer is now owned by canon.  */
+                 canonbuf = NULL;
                else
                  {
                    canon = __strdup (canon);
@@ -1215,8 +1191,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
   if (malloc_name)
     free ((char *) name);
   free (addrmem);
-  if (malloc_canonbuf)
-    free (canonbuf);
+  free (canonbuf);
 
   return result;
 }