Submitted By:            Xi Ruoyao <xry111 at xry111.site>
Date:                    2023-09-13
Initial Package Version: 2.36
Upstream Status:         Under review
Origin:      https://sourceware.org/ml/libc-alpha/2023-September/151548.html
Description:             Fixes a security vulnerability in Glibc-2.36 and
                         2.37 as shipped by LFS 11.2 and 11.3.  This
                         vulnerability allow denial of service with custom
                         NSS modules and extremely rare conditions.  Glibc
                         releases earlier than 2.36 are also affected but
                         there is no fix available for earlier releases yet.

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 6ae6744fe4..eb5ba59dac 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -120,6 +120,7 @@ struct gaih_result
 {
   struct gaih_addrtuple *at;
   char *canon;
+  char *hname;
   bool free_at;
   bool got_ipv6;
 };
@@ -165,6 +166,7 @@ gaih_result_reset (struct gaih_result *res)
   if (res->free_at)
     free (res->at);
   free (res->canon);
+  free (res->hname);
   memset (res, 0, sizeof (*res));
 }
 
@@ -203,9 +205,8 @@ gaih_inet_serv (const char *servicename, const struct gaih_typeproto *tp,
   return 0;
 }
 
-/* Convert struct hostent to a list of struct gaih_addrtuple objects.  h_name
-   is not copied, and the struct hostent object must not be deallocated
-   prematurely.  The new addresses are appended to the tuple array in RES.  */
+/* Convert struct hostent to a list of struct gaih_addrtuple objects.  The new
+   addresses are appended to the tuple array in RES.  */
 static bool
 convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, int family,
 				   struct hostent *h, struct gaih_result *res)
@@ -238,6 +239,15 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, int family,
   res->at = array;
   res->free_at = true;
 
+  /* Duplicate h_name because it may get reclaimed when the underlying storage
+     is freed.  */
+  if (res->hname == NULL)
+    {
+      res->hname = __strdup (h->h_name);
+      if (res->hname == NULL)
+	return false;
+    }
+
   /* Update the next pointers on reallocation.  */
   for (size_t i = 0; i < old; i++)
     array[i].next = array + i + 1;
@@ -262,7 +272,6 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, int family,
 	}
       array[i].next = array + i + 1;
     }
-  array[0].name = h->h_name;
   array[count - 1].next = NULL;
 
   return true;
@@ -324,15 +333,15 @@ gethosts (nss_gethostbyname3_r fct, int family, const char *name,
    memory allocation failure.  The returned string is allocated on the
    heap; the caller has to free it.  */
 static char *
-getcanonname (nss_action_list nip, struct gaih_addrtuple *at, const char *name)
+getcanonname (nss_action_list nip, const char *hname, const char *name)
 {
   nss_getcanonname_r *cfct = __nss_lookup_function (nip, "getcanonname_r");
   char *s = (char *) name;
   if (cfct != NULL)
     {
       char buf[256];
-      if (DL_CALL_FCT (cfct, (at->name ?: name, buf, sizeof (buf),
-			      &s, &errno, &h_errno)) != NSS_STATUS_SUCCESS)
+      if (DL_CALL_FCT (cfct, (hname ?: name, buf, sizeof (buf), &s, &errno,
+			      &h_errno)) != NSS_STATUS_SUCCESS)
 	/* If the canonical name cannot be determined, use the passed
 	   string.  */
 	s = (char *) name;
@@ -740,6 +749,7 @@ get_nss_addresses (const char *name, const struct addrinfo *req,
 		    }
 		  no_inet6_data = no_data;
 		  inet6_status = status;
+
 		}
 	      if (req->ai_family == AF_INET
 		  || req->ai_family == AF_UNSPEC
@@ -771,7 +781,7 @@ get_nss_addresses (const char *name, const struct addrinfo *req,
 		  if ((req->ai_flags & AI_CANONNAME) != 0
 		      && res->canon == NULL)
 		    {
-		      char *canonbuf = getcanonname (nip, res->at, name);
+		      char *canonbuf = getcanonname (nip, res->hname, name);
 		      if (canonbuf == NULL)
 			{
 			  __resolv_context_put (res_ctx);