From 228cdb00a045ae3b68a91b35c7548bab6029446e Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Thu, 17 Mar 2022 11:44:34 +0530
Subject: [PATCH] Simplify allocations and fix merge and continue actions [BZ
 #28931]

Allocations for address tuples is currently a bit confusing because of
the pointer chasing through PAT, making it hard to observe the sequence
in which allocations have been made.  Narrow scope of the pointer
chasing through PAT so that it is only used where necessary.

This also tightens actions behaviour with the hosts database in
getaddrinfo to comply with the manual text.  The "continue" action
discards previous results and the "merge" action results in an immedate
lookup failure.  Consequently, chaining of allocations across modules is
no longer necessary, thus opening up cleanup opportunities.

A test has been added that checks some combinations to ensure that they
work correctly.

Resolves: BZ #28931

---
 sysdeps/posix/getaddrinfo.c | 143 +++++++++++++++++++++++-------------
 1 file changed, 91 insertions(+), 52 deletions(-)

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 9f1cde27..702d8a50 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -458,11 +458,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
   if (name != NULL)
     {
-      at = alloca_account (sizeof (struct gaih_addrtuple), alloca_used);
-      at->family = AF_UNSPEC;
-      at->scopeid = 0;
-      at->next = NULL;
-
       if (req->ai_flags & AI_IDN)
 	{
 	  char *out;
@@ -473,13 +468,21 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	  malloc_name = true;
 	}
 
-      if (__inet_aton_exact (name, (struct in_addr *) at->addr) != 0)
+      uint32_t addr[4];
+      if (__inet_aton_exact (name, (struct in_addr *) addr) != 0)
 	{
+	  at = alloca_account (sizeof (struct gaih_addrtuple), alloca_used);
+	  at->scopeid = 0;
+	  at->next = NULL;
+
 	  if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET)
-	    at->family = AF_INET;
+	    {
+	      memcpy (at->addr, addr, sizeof (at->addr));
+	      at->family = AF_INET;
+	    }
 	  else if (req->ai_family == AF_INET6 && (req->ai_flags & AI_V4MAPPED))
 	    {
-	      at->addr[3] = at->addr[0];
+	      at->addr[3] = addr[0];
 	      at->addr[2] = htonl (0xffff);
 	      at->addr[1] = 0;
 	      at->addr[0] = 0;
@@ -493,49 +496,62 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
 	  if (req->ai_flags & AI_CANONNAME)
 	    canon = name;
+
+	  goto process_list;
 	}
-      else if (at->family == AF_UNSPEC)
+
+      char *scope_delim = strchr (name, SCOPE_DELIMITER);
+      int e;
+
+      if (scope_delim == NULL)
+	e = inet_pton (AF_INET6, name, addr);
+      else
+	e = __inet_pton_length (AF_INET6, name, scope_delim - name, addr);
+
+      if (e > 0)
 	{
-	  char *scope_delim = strchr (name, SCOPE_DELIMITER);
-	  int e;
-	  if (scope_delim == NULL)
-	    e = inet_pton (AF_INET6, name, at->addr);
+	  at = alloca_account (sizeof (struct gaih_addrtuple),
+			       alloca_used);
+	  at->scopeid = 0;
+	  at->next = NULL;
+
+	  if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET6)
+	    {
+	      memcpy (at->addr, addr, sizeof (at->addr));
+	      at->family = AF_INET6;
+	    }
+	  else if (req->ai_family == AF_INET
+		   && IN6_IS_ADDR_V4MAPPED (addr))
+	    {
+	      at->addr[0] = addr[3];
+	      at->addr[1] = addr[1];
+	      at->addr[2] = addr[2];
+	      at->addr[3] = addr[3];
+	      at->family = AF_INET;
+	    }
 	  else
-	    e = __inet_pton_length (AF_INET6, name, scope_delim - name,
-				    at->addr);
-	  if (e > 0)
 	    {
-	      if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET6)
-		at->family = AF_INET6;
-	      else if (req->ai_family == AF_INET
-		       && IN6_IS_ADDR_V4MAPPED (at->addr))
-		{
-		  at->addr[0] = at->addr[3];
-		  at->family = AF_INET;
-		}
-	      else
-		{
-		  result = -EAI_ADDRFAMILY;
-		  goto free_and_return;
-		}
-
-	      if (scope_delim != NULL
-		  && __inet6_scopeid_pton ((struct in6_addr *) at->addr,
-					   scope_delim + 1,
-					   &at->scopeid) != 0)
-		{
-		  result = -EAI_NONAME;
-		  goto free_and_return;
-		}
+	      result = -EAI_ADDRFAMILY;
+	      goto free_and_return;
+	    }
 
-	      if (req->ai_flags & AI_CANONNAME)
-		canon = name;
+	  if (scope_delim != NULL
+	      && __inet6_scopeid_pton ((struct in6_addr *) at->addr,
+				       scope_delim + 1,
+				       &at->scopeid) != 0)
+	    {
+	      result = -EAI_NONAME;
+	      goto free_and_return;
 	    }
+
+	  if (req->ai_flags & AI_CANONNAME)
+	    canon = name;
+
+	  goto process_list;
 	}
 
-      if (at->family == AF_UNSPEC && (req->ai_flags & AI_NUMERICHOST) == 0)
+      if ((req->ai_flags & AI_NUMERICHOST) == 0)
 	{
-	  struct gaih_addrtuple **pat = &at;
 	  int no_data = 0;
 	  int no_inet6_data = 0;
 	  nss_action_list nip;
@@ -543,6 +559,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	  enum nss_status status = NSS_STATUS_UNAVAIL;
 	  int no_more;
 	  struct resolv_context *res_ctx = NULL;
+	  bool do_merge = false;
 
 	  /* If we do not have to look for IPv6 addresses or the canonical
 	     name, use the simple, old functions, which do not support
@@ -579,7 +596,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 			  result = -EAI_MEMORY;
 			  goto free_and_return;
 			}
-		      *pat = addrmem;
+		      at = addrmem;
 		    }
 		  else
 		    {
@@ -632,6 +649,8 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		    }
 
 		  struct gaih_addrtuple *addrfree = addrmem;
+		  struct gaih_addrtuple **pat = &at;
+
 		  for (int i = 0; i < air->naddrs; ++i)
 		    {
 		      socklen_t size = (air->family[i] == AF_INET
@@ -695,12 +714,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
 		  free (air);
 
-		  if (at->family == AF_UNSPEC)
-		    {
-		      result = -EAI_NONAME;
-		      goto free_and_return;
-		    }
-
 		  goto process_list;
 		}
 	      else if (err == 0)
@@ -732,6 +745,22 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
 	  while (!no_more)
 	    {
+	      /* Always start afresh; continue should discard previous results
+		 and the hosts database does not support merge.  */
+	      at = NULL;
+	      free (canonbuf);
+	      free (addrmem);
+	      canon = canonbuf = NULL;
+	      addrmem = NULL;
+	      got_ipv6 = false;
+
+	      if (do_merge)
+		{
+		  __set_h_errno (NETDB_INTERNAL);
+		  __set_errno (EBUSY);
+		  break;
+		}
+
 	      no_data = 0;
 	      nss_gethostbyname4_r *fct4 = NULL;
 
@@ -744,12 +773,14 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		{
 		  while (1)
 		    {
-		      status = DL_CALL_FCT (fct4, (name, pat,
+		      status = DL_CALL_FCT (fct4, (name, &at,
 						   tmpbuf->data, tmpbuf->length,
 						   &errno, &h_errno,
 						   NULL));
 		      if (status == NSS_STATUS_SUCCESS)
 			break;
+		      /* gethostbyname4_r may write into AT, so reset it.  */
+		      at = NULL;
 		      if (status != NSS_STATUS_TRYAGAIN
 			  || errno != ERANGE || h_errno != NETDB_INTERNAL)
 			{
@@ -774,7 +805,9 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		      no_data = 1;
 
 		      if ((req->ai_flags & AI_CANONNAME) != 0 && canon == NULL)
-			canon = (*pat)->name;
+			canon = at->name;
+
+		      struct gaih_addrtuple **pat = &at;
 
 		      while (*pat != NULL)
 			{
@@ -826,6 +859,8 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
 		  if (fct != NULL)
 		    {
+		      struct gaih_addrtuple **pat = &at;
+
 		      if (req->ai_family == AF_INET6
 			  || req->ai_family == AF_UNSPEC)
 			{
@@ -899,6 +934,10 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	      if (nss_next_action (nip, status) == NSS_ACTION_RETURN)
 		break;
 
+	      /* The hosts database does not support MERGE.  */
+	      if (nss_next_action (nip, status) == NSS_ACTION_MERGE)
+		do_merge = true;
+
 	      nip++;
 	      if (nip->module == NULL)
 		no_more = -1;
@@ -930,7 +969,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	}
 
     process_list:
-      if (at->family == AF_UNSPEC)
+      if (at == NULL)
 	{
 	  result = -EAI_NONAME;
 	  goto free_and_return;
-- 
2.33.0

