commit 228cdb00a045ae3b68a91b35c7548bab6029446e
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Thu Mar 17 11:44:34 2022 +0530

    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
    
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
    Reviewed-by: DJ Delorie <dj@redhat.com>
    (cherry picked from commit 1c37b8022e8763fedbb3f79c02e05c6acfe5a215)

Conflicts:
	nss/Makefile
	(Missing test cases)
	sysdeps/posix/getaddrinfo.c
	(RES_USE_INET6 still present in RHEL-8 and NSS module traversal rewrite
	not in RHEL-8)

diff --git a/nss/Makefile b/nss/Makefile
index e8a7d9c7b3cefcdf..cfb255c6e7a3a4de 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -65,7 +65,8 @@ xtests			= bug-erange
 
 tests-container = \
 			  tst-nss-db-endpwent \
-			  tst-nss-db-endgrent
+			  tst-nss-db-endgrent \
+			  tst-nss-gai-actions
 
 # Tests which need libdl
 ifeq (yes,$(build-shared))
diff --git a/nss/tst-nss-gai-actions.c b/nss/tst-nss-gai-actions.c
new file mode 100644
index 0000000000000000..efca6cd1837a172a
--- /dev/null
+++ b/nss/tst-nss-gai-actions.c
@@ -0,0 +1,149 @@
+/* Test continue and merge NSS actions for getaddrinfo.
+   Copyright The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <gnu/lib-names.h>
+#include <nss.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/support.h>
+#include <support/xstdio.h>
+#include <support/xunistd.h>
+
+enum
+{
+  ACTION_MERGE = 0,
+  ACTION_CONTINUE,
+};
+
+static const char *
+family_str (int family)
+{
+  switch (family)
+    {
+    case AF_UNSPEC:
+      return "AF_UNSPEC";
+    case AF_INET:
+      return "AF_INET";
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static const char *
+action_str (int action)
+{
+  switch (action)
+    {
+    case ACTION_MERGE:
+      return "merge";
+    case ACTION_CONTINUE:
+      return "continue";
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static void
+do_one_test (int action, int family, bool canon)
+{
+  struct addrinfo hints =
+    {
+      .ai_family = family,
+    };
+
+  struct addrinfo *ai;
+
+  if (canon)
+    hints.ai_flags = AI_CANONNAME;
+
+  printf ("***** Testing \"files [SUCCESS=%s] files\" for family %s, %s\n",
+	  action_str (action), family_str (family),
+	  canon ? "AI_CANONNAME" : "");
+
+  int ret = getaddrinfo ("example.org", "80", &hints, &ai);
+
+  switch (action)
+    {
+    case ACTION_MERGE:
+      if (ret == 0)
+	{
+	  char *formatted = support_format_addrinfo (ai, ret);
+
+	  printf ("merge unexpectedly succeeded:\n %s\n", formatted);
+	  support_record_failure ();
+	  free (formatted);
+	}
+      else
+	return;
+    case ACTION_CONTINUE:
+	{
+	  char *formatted = support_format_addrinfo (ai, ret);
+
+	  /* Verify that the result appears exactly once.  */
+	  const char *expected = "address: STREAM/TCP 192.0.0.1 80\n"
+	    "address: DGRAM/UDP 192.0.0.1 80\n"
+	    "address: RAW/IP 192.0.0.1 80\n";
+
+	  const char *contains = strstr (formatted, expected);
+	  const char *contains2 = NULL;
+
+	  if (contains != NULL)
+	    contains2 = strstr (contains + strlen (expected), expected);
+
+	  if (contains == NULL || contains2 != NULL)
+	    {
+	      printf ("continue failed:\n%s\n", formatted);
+	      support_record_failure ();
+	    }
+
+	  free (formatted);
+	  break;
+	}
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static void
+do_one_test_set (int action)
+{
+  char buf[32];
+
+  snprintf (buf, sizeof (buf), "files [SUCCESS=%s] files",
+	    action_str (action));
+  __nss_configure_lookup ("hosts", buf);
+
+  do_one_test (action, AF_UNSPEC, false);
+  do_one_test (action, AF_INET, false);
+  do_one_test (action, AF_INET, true);
+}
+
+static int
+do_test (void)
+{
+  do_one_test_set (ACTION_CONTINUE);
+  do_one_test_set (ACTION_MERGE);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/nss/tst-nss-gai-actions.root/etc/host.conf b/nss/tst-nss-gai-actions.root/etc/host.conf
new file mode 100644
index 0000000000000000..d1a59f73a90f2993
--- /dev/null
+++ b/nss/tst-nss-gai-actions.root/etc/host.conf
@@ -0,0 +1 @@
+multi on
diff --git a/nss/tst-nss-gai-actions.root/etc/hosts b/nss/tst-nss-gai-actions.root/etc/hosts
new file mode 100644
index 0000000000000000..50ce9774dc2c21d9
--- /dev/null
+++ b/nss/tst-nss-gai-actions.root/etc/hosts
@@ -0,0 +1,508 @@
+192.0.0.1	example.org
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+192.0.1.158	example.org
+192.0.1.159	example.org
+192.0.1.160	example.org
+192.0.1.161	example.org
+192.0.1.162	example.org
+192.0.1.163	example.org
+192.0.1.164	example.org
+192.0.1.165	example.org
+192.0.1.166	example.org
+192.0.1.167	example.org
+192.0.1.168	example.org
+192.0.1.169	example.org
+192.0.1.170	example.org
+192.0.1.171	example.org
+192.0.1.172	example.org
+192.0.1.173	example.org
+192.0.1.174	example.org
+192.0.1.175	example.org
+192.0.1.176	example.org
+192.0.1.177	example.org
+192.0.1.178	example.org
+192.0.1.179	example.org
+192.0.1.180	example.org
+192.0.1.181	example.org
+192.0.1.182	example.org
+192.0.1.183	example.org
+192.0.1.184	example.org
+192.0.1.185	example.org
+192.0.1.186	example.org
+192.0.1.187	example.org
+192.0.1.188	example.org
+192.0.1.189	example.org
+192.0.1.190	example.org
+192.0.1.191	example.org
+192.0.1.192	example.org
+192.0.1.193	example.org
+192.0.1.194	example.org
+192.0.1.195	example.org
+192.0.1.196	example.org
+192.0.1.197	example.org
+192.0.1.198	example.org
+192.0.1.199	example.org
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+192.0.1.201	example.org
+192.0.1.202	example.org
+192.0.1.203	example.org
+192.0.1.204	example.org
+192.0.1.205	example.org
+192.0.1.206	example.org
+192.0.1.207	example.org
+192.0.1.208	example.org
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+192.0.1.216	example.org
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+192.0.1.221	example.org
+192.0.1.222	example.org
+192.0.1.223	example.org
+192.0.1.224	example.org
+192.0.1.225	example.org
+192.0.1.226	example.org
+192.0.1.227	example.org
+192.0.1.228	example.org
+192.0.1.229	example.org
+192.0.1.230	example.org
+192.0.1.231	example.org
+192.0.1.232	example.org
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+192.0.1.234	example.org
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+192.0.1.238	example.org
+192.0.1.239	example.org
+192.0.1.240	example.org
+192.0.1.241	example.org
+192.0.1.242	example.org
+192.0.1.243	example.org
+192.0.1.244	example.org
+192.0.1.245	example.org
+192.0.1.246	example.org
+192.0.1.247	example.org
+192.0.1.248	example.org
+192.0.1.249	example.org
+192.0.1.250	example.org
+192.0.1.251	example.org
+192.0.1.252	example.org
+192.0.1.253	example.org
+192.0.1.254	example.org
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index fae3dea81f19dba6..4fa963644af8b7d5 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -474,11 +474,6 @@ 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;
@@ -489,13 +484,21 @@ 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;
@@ -509,49 +512,62 @@ 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;
 	  service_user *nip;
@@ -560,6 +576,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	  int no_more;
 	  struct resolv_context *res_ctx = NULL;
 	  bool res_enable_inet6 = false;
+	  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
@@ -596,7 +613,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 			  result = -EAI_MEMORY;
 			  goto free_and_return;
 			}
-		      *pat = addrmem;
+		      at = addrmem;
 		    }
 		  else
 		    {
@@ -649,6 +666,8 @@ 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
@@ -712,12 +731,6 @@ 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)
@@ -756,6 +769,22 @@ 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;
 
@@ -768,12 +797,14 @@ 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)
 			{
@@ -800,7 +831,9 @@ 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)
 			{
@@ -852,6 +885,8 @@ 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)
 			{
@@ -927,6 +962,10 @@ 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;
+
 	      if (nip->next == NULL)
 		no_more = -1;
 	      else
@@ -960,7 +999,7 @@ 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;
