glibc: add security patches

Fix for 2.21 and 2.22:
CVE-2015-7547 - glibc getaddrinfo stack-based buffer overflow.

For 2.21:
CVE-2014-8121 - Unexpected closing of nss_files databases after lookups
causes denial of service.
CVE-2015-1781 - buffer overflow in gethostbyname_r() and related
functions with misaligned buffer.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/glibc/2.21/0001-fix-CVE-2015-7547.patch

@@ -0,0 +1,236 @@
+Fetched from gentoo glibc patchball
+Original patch filename: 10_all_glibc-CVE-2015-7547.patch
+Based on: https://sourceware.org/ml/libc-alpha/2016-02/msg00416.html
+
+Fixes:
+CVE-2015-7547 - glibc getaddrinfo stack-based buffer overflow.
+
+Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
+
+--- a/resolv/nss_dns/dns-host.c
++++ b/resolv/nss_dns/dns-host.c
+@@ -1031,7 +1031,10 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
+   int h_namelen = 0;
+ 
+   if (ancount == 0)
+-    return NSS_STATUS_NOTFOUND;
++    {
++      *h_errnop = HOST_NOT_FOUND;
++      return NSS_STATUS_NOTFOUND;
++    }
+ 
+   while (ancount-- > 0 && cp < end_of_message && had_error == 0)
+     {
+@@ -1208,7 +1211,14 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
+   /* Special case here: if the resolver sent a result but it only
+      contains a CNAME while we are looking for a T_A or T_AAAA record,
+      we fail with NOTFOUND instead of TRYAGAIN.  */
+-  return canon == NULL ? NSS_STATUS_TRYAGAIN : NSS_STATUS_NOTFOUND;
++  if (canon != NULL)
++    {
++      *h_errnop = HOST_NOT_FOUND;
++      return NSS_STATUS_NOTFOUND;
++    }
++
++  *h_errnop = NETDB_INTERNAL;
++  return NSS_STATUS_TRYAGAIN;
+ }
+ 
+ 
+@@ -1242,8 +1252,15 @@ gaih_getanswer (const querybuf *answer1, int anslen1, const querybuf *answer2,
+ 						     &pat, &buffer, &buflen,
+ 						     errnop, h_errnop, ttlp,
+ 						     &first);
++      /* Use the second response status in some cases.  */
+       if (status != NSS_STATUS_SUCCESS && status2 != NSS_STATUS_NOTFOUND)
+ 	status = status2;
++      /* Do not return a truncated second response (unless it was
++         unavoidable e.g. unrecoverable TRYAGAIN).  */
++      if (status == NSS_STATUS_SUCCESS
++	  && (status2 == NSS_STATUS_TRYAGAIN
++	      && *errnop == ERANGE && *h_errnop != NO_RECOVERY))
++	status = NSS_STATUS_TRYAGAIN;
+     }
+ 
+   return status;
+--- a/resolv/res_query.c
++++ b/resolv/res_query.c
+@@ -396,6 +396,7 @@ __libc_res_nsearch(res_state statp,
+ 		  {
+ 		    free (*answerp2);
+ 		    *answerp2 = NULL;
++		    *nanswerp2 = 0;
+ 		    *answerp2_malloced = 0;
+ 		  }
+ 	}
+@@ -447,6 +448,7 @@ __libc_res_nsearch(res_state statp,
+ 			  {
+ 			    free (*answerp2);
+ 			    *answerp2 = NULL;
++			    *nanswerp2 = 0;
+ 			    *answerp2_malloced = 0;
+ 			  }
+ 
+@@ -521,6 +523,7 @@ __libc_res_nsearch(res_state statp,
+ 	  {
+ 	    free (*answerp2);
+ 	    *answerp2 = NULL;
++	    *nanswerp2 = 0;
+ 	    *answerp2_malloced = 0;
+ 	  }
+ 	if (saved_herrno != -1)
+--- a/resolv/res_send.c
++++ b/resolv/res_send.c
+@@ -639,11 +639,7 @@ send_vc(res_state statp,
+ {
+ 	const HEADER *hp = (HEADER *) buf;
+ 	const HEADER *hp2 = (HEADER *) buf2;
+-	u_char *ans = *ansp;
+-	int orig_anssizp = *anssizp;
+-	// XXX REMOVE
+-	// int anssiz = *anssizp;
+-	HEADER *anhp = (HEADER *) ans;
++	HEADER *anhp = (HEADER *) *ansp;
+ 	struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns];
+ 	int truncating, connreset, n;
+ 	/* On some architectures compiler might emit a warning indicating
+@@ -767,35 +763,6 @@ send_vc(res_state statp,
+ 		assert (anscp != NULL || ansp2 == NULL);
+ 		thisresplenp = &resplen;
+ 	} else {
+-		if (*anssizp != MAXPACKET) {
+-			/* No buffer allocated for the first
+-			   reply.  We can try to use the rest
+-			   of the user-provided buffer.  */
+-#if __GNUC_PREREQ (4, 7)
+-			DIAG_PUSH_NEEDS_COMMENT;
+-			DIAG_IGNORE_NEEDS_COMMENT (5, "-Wmaybe-uninitialized");
+-#endif
+-#if _STRING_ARCH_unaligned
+-			*anssizp2 = orig_anssizp - resplen;
+-			*ansp2 = *ansp + resplen;
+-#else
+-			int aligned_resplen
+-			  = ((resplen + __alignof__ (HEADER) - 1)
+-			     & ~(__alignof__ (HEADER) - 1));
+-			*anssizp2 = orig_anssizp - aligned_resplen;
+-			*ansp2 = *ansp + aligned_resplen;
+-#endif
+-#if __GNUC_PREREQ (4, 7)
+-			DIAG_POP_NEEDS_COMMENT;
+-#endif
+-		} else {
+-			/* The first reply did not fit into the
+-			   user-provided buffer.  Maybe the second
+-			   answer will.  */
+-			*anssizp2 = orig_anssizp;
+-			*ansp2 = *ansp;
+-		}
+-
+ 		thisanssizp = anssizp2;
+ 		thisansp = ansp2;
+ 		thisresplenp = resplen2;
+@@ -804,10 +771,14 @@ send_vc(res_state statp,
+ 	anhp = (HEADER *) *thisansp;
+ 
+ 	*thisresplenp = rlen;
+-	if (rlen > *thisanssizp) {
+-		/* Yes, we test ANSCP here.  If we have two buffers
+-		   both will be allocatable.  */
+-		if (__glibc_likely (anscp != NULL))       {
++	/* Is the answer buffer too small?  */
++	if (*thisanssizp < rlen) {
++		/* If the current buffer is not the the static
++		   user-supplied buffer then we can reallocate
++		   it.  */
++		if (thisansp != NULL && thisansp != ansp) {
++			/* Always allocate MAXPACKET, callers expect
++			   this specific size.  */
+ 			u_char *newp = malloc (MAXPACKET);
+ 			if (newp == NULL) {
+ 				*terrno = ENOMEM;
+@@ -957,8 +928,6 @@ send_dg(res_state statp,
+ {
+ 	const HEADER *hp = (HEADER *) buf;
+ 	const HEADER *hp2 = (HEADER *) buf2;
+-	u_char *ans = *ansp;
+-	int orig_anssizp = *anssizp;
+ 	struct timespec now, timeout, finish;
+ 	struct pollfd pfd[1];
+ 	int ptimeout;
+@@ -1154,50 +1123,48 @@ send_dg(res_state statp,
+ 			assert (anscp != NULL || ansp2 == NULL);
+ 			thisresplenp = &resplen;
+ 		} else {
+-			if (*anssizp != MAXPACKET) {
+-				/* No buffer allocated for the first
+-				   reply.  We can try to use the rest
+-				   of the user-provided buffer.  */
+-#if _STRING_ARCH_unaligned
+-				*anssizp2 = orig_anssizp - resplen;
+-				*ansp2 = *ansp + resplen;
+-#else
+-				int aligned_resplen
+-				  = ((resplen + __alignof__ (HEADER) - 1)
+-				     & ~(__alignof__ (HEADER) - 1));
+-				*anssizp2 = orig_anssizp - aligned_resplen;
+-				*ansp2 = *ansp + aligned_resplen;
+-#endif
+-			} else {
+-				/* The first reply did not fit into the
+-				   user-provided buffer.  Maybe the second
+-				   answer will.  */
+-				*anssizp2 = orig_anssizp;
+-				*ansp2 = *ansp;
+-			}
+-
+ 			thisanssizp = anssizp2;
+ 			thisansp = ansp2;
+ 			thisresplenp = resplen2;
+ 		}
+ 
+ 		if (*thisanssizp < MAXPACKET
+-		    /* Yes, we test ANSCP here.  If we have two buffers
+-		       both will be allocatable.  */
+-		    && anscp
++		    /* If the current buffer is not the the static
++		       user-supplied buffer then we can reallocate
++		       it.  */
++		    && (thisansp != NULL && thisansp != ansp)
+ #ifdef FIONREAD
++		    /* Is the size too small?  */
+ 		    && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0
+ 			|| *thisanssizp < *thisresplenp)
+ #endif
+                     ) {
++			/* Always allocate MAXPACKET, callers expect
++			   this specific size.  */
+ 			u_char *newp = malloc (MAXPACKET);
+ 			if (newp != NULL) {
+-				*anssizp = MAXPACKET;
+-				*thisansp = ans = newp;
++				*thisanssizp = MAXPACKET;
++				*thisansp = newp;
+ 				if (thisansp == ansp2)
+ 				  *ansp2_malloced = 1;
+ 			}
+ 		}
++		/* We could end up with truncation if anscp was NULL
++		   (not allowed to change caller's buffer) and the
++		   response buffer size is too small.  This isn't a
++		   reliable way to detect truncation because the ioctl
++		   may be an inaccurate report of the UDP message size.
++		   Therefore we use this only to issue debug output.
++		   To do truncation accurately with UDP we need
++		   MSG_TRUNC which is only available on Linux.  We
++		   can abstract out the Linux-specific feature in the
++		   future to detect truncation.  */
++		if (__glibc_unlikely (*thisanssizp < *thisresplenp)) {
++			Dprint(statp->options & RES_DEBUG,
++			       (stdout, ";; response may be truncated (UDP)\n")
++			);
++		}
++
+ 		HEADER *anhp = (HEADER *) *thisansp;
+ 		socklen_t fromlen = sizeof(struct sockaddr_in6);
+ 		assert (sizeof(from) <= fromlen);

package/glibc/2.21/0002-fix-CVE-2015-1781.patch

@@ -0,0 +1,32 @@
+From 10c6d2e3243cefdd22933d3706f53d9f913c6cab Mon Sep 17 00:00:00 2001
+From: Arjun Shankar <arjun.is@lostca.se>
+Date: Tue, 21 Apr 2015 14:06:31 +0200
+Subject: [PATCH] CVE-2015-1781: resolv/nss_dns/dns-host.c buffer overflow
+ [BZ#18287]
+
+Fixes:
+CVE-2015-1781 - buffer overflow in gethostbyname_r() and related
+functions with misaligned buffer.
+
+Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
+---
+ resolv/nss_dns/dns-host.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
+index f715ab0..40069a7 100644
+--- a/resolv/nss_dns/dns-host.c
++++ b/resolv/nss_dns/dns-host.c
+@@ -615,7 +615,8 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
+   int have_to_map = 0;
+   uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
+   buffer += pad;
+-  if (__glibc_unlikely (buflen < sizeof (struct host_data) + pad))
++  buflen = buflen > pad ? buflen - pad : 0;
++  if (__glibc_unlikely (buflen < sizeof (struct host_data)))
+     {
+       /* The buffer is too small.  */
+     too_small:
+-- 
+2.4.4
+

package/glibc/2.21/0003-fix-CVE-2014-8121.patch

@@ -0,0 +1,176 @@
+From 6d0b7b443c9735672bb76d003c3f7263c5292d7d Mon Sep 17 00:00:00 2001
+From: Florian Weimer <fweimer@redhat.com>
+Date: Wed, 29 Apr 2015 14:41:25 +0200
+Subject: [PATCH 23/27] CVE-2014-8121: Do not close NSS files database during
+ iteration [BZ #18007]
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+(cherry picked from commit e871e19b5f19d2e6595e911b0a5b1c19cda20cc7)
+
+Fixes:
+CVE-2014-8121 - Unexpected closing of nss_files databases after lookups
+causes denial of service.
+
+Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
+---
+ nss/Makefile              |   2 +-
+ nss/nss_files/files-XXX.c |   2 +-
+ nss/tst-nss-getpwent.c    | 118 ++++++++++++++++++++++++++++++++++++++++++++++
+ 3 files changed, 120 insertions(+), 2 deletions(-)
+ create mode 100644 nss/tst-nss-getpwent.c
+
+diff --git a/nss/Makefile b/nss/Makefile
+index d419baf..dc351dd 100644
+--- a/nss/Makefile
++++ b/nss/Makefile
+@@ -39,7 +39,7 @@ install-bin             := getent makedb
+ makedb-modules = xmalloc hash-string
+ extra-objs		+= $(makedb-modules:=.o)
+ 
+-tests			= test-netdb tst-nss-test1 test-digits-dots
++tests			= test-netdb tst-nss-test1 test-digits-dots tst-nss-getpwent
+ xtests			= bug-erange
+ 
+ # Specify rules for the nss_* modules.  We have some services.
+diff --git a/nss/nss_files/files-XXX.c b/nss/nss_files/files-XXX.c
+index a7a45e5..a7ce5ea 100644
+--- a/nss/nss_files/files-XXX.c
++++ b/nss/nss_files/files-XXX.c
+@@ -134,7 +134,7 @@ CONCAT(_nss_files_set,ENTNAME) (int stayopen)
+ 
+   __libc_lock_lock (lock);
+ 
+-  status = internal_setent (stayopen);
++  status = internal_setent (1);
+ 
+   if (status == NSS_STATUS_SUCCESS && fgetpos (stream, &position) < 0)
+     {
+diff --git a/nss/tst-nss-getpwent.c b/nss/tst-nss-getpwent.c
+new file mode 100644
+index 0000000..f2e8abc
+--- /dev/null
++++ b/nss/tst-nss-getpwent.c
+@@ -0,0 +1,118 @@
++/* Copyright (C) 2015 Free Software Foundation, Inc.
++   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
++   <http://www.gnu.org/licenses/>.  */
++
++#include <pwd.h>
++#include <stdbool.h>
++#include <stdio.h>
++#include <stdlib.h>
++#include <string.h>
++
++int
++do_test (void)
++{
++  /* Count the number of entries in the password database, and fetch
++     data from the first and last entries.  */
++  size_t count = 0;
++  struct passwd * pw;
++  char *first_name = NULL;
++  uid_t first_uid = 0;
++  char *last_name = NULL;
++  uid_t last_uid = 0;
++  setpwent ();
++  while ((pw  = getpwent ()) != NULL)
++    {
++      if (first_name == NULL)
++	{
++	  first_name = strdup (pw->pw_name);
++	  if (first_name == NULL)
++	    {
++	      printf ("strdup: %m\n");
++	      return 1;
++	    }
++	  first_uid = pw->pw_uid;
++	}
++
++      free (last_name);
++      last_name = strdup (pw->pw_name);
++      if (last_name == NULL)
++	{
++	  printf ("strdup: %m\n");
++	  return 1;
++	}
++      last_uid = pw->pw_uid;
++      ++count;
++    }
++  endpwent ();
++
++  if (count == 0)
++    {
++      printf ("No entries in the password database.\n");
++      return 0;
++    }
++
++  /* Try again, this time interleaving with name-based and UID-based
++     lookup operations.  The counts do not match if the interleaved
++     lookups affected the enumeration.  */
++  size_t new_count = 0;
++  setpwent ();
++  while ((pw  = getpwent ()) != NULL)
++    {
++      if (new_count == count)
++	{
++	  printf ("Additional entry in the password database.\n");
++	  return 1;
++	}
++      ++new_count;
++      struct passwd *pw2 = getpwnam (first_name);
++      if (pw2 == NULL)
++	{
++	  printf ("getpwnam (%s) failed: %m\n", first_name);
++	  return 1;
++	}
++      pw2 = getpwnam (last_name);
++      if (pw2 == NULL)
++	{
++	  printf ("getpwnam (%s) failed: %m\n", last_name);
++	  return 1;
++	}
++      pw2 = getpwuid (first_uid);
++      if (pw2 == NULL)
++	{
++	  printf ("getpwuid (%llu) failed: %m\n",
++		  (unsigned long long) first_uid);
++	  return 1;
++	}
++      pw2 = getpwuid (last_uid);
++      if (pw2 == NULL)
++	{
++	  printf ("getpwuid (%llu) failed: %m\n",
++		  (unsigned long long) last_uid);
++	  return 1;
++	}
++    }
++  endpwent ();
++  if (new_count < count)
++    {
++      printf ("Missing entry in the password database.\n");
++      return 1;
++    }
++
++  return 0;
++}
++
++#define TEST_FUNCTION do_test ()
++#include "../test-skeleton.c"
+-- 
+2.6.2
+

package/glibc/2.22/0001-fix-CVE-2015-7547.patch

@@ -0,0 +1,236 @@
+Fetched from gentoo glibc patchball
+Original patch filename: 10_all_glibc-CVE-2015-7547.patch
+Based on: https://sourceware.org/ml/libc-alpha/2016-02/msg00416.html
+
+Fixes:
+CVE-2015-7547 - glibc getaddrinfo stack-based buffer overflow.
+
+Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
+
+--- a/resolv/nss_dns/dns-host.c
++++ b/resolv/nss_dns/dns-host.c
+@@ -1031,7 +1031,10 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
+   int h_namelen = 0;
+ 
+   if (ancount == 0)
+-    return NSS_STATUS_NOTFOUND;
++    {
++      *h_errnop = HOST_NOT_FOUND;
++      return NSS_STATUS_NOTFOUND;
++    }
+ 
+   while (ancount-- > 0 && cp < end_of_message && had_error == 0)
+     {
+@@ -1208,7 +1211,14 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
+   /* Special case here: if the resolver sent a result but it only
+      contains a CNAME while we are looking for a T_A or T_AAAA record,
+      we fail with NOTFOUND instead of TRYAGAIN.  */
+-  return canon == NULL ? NSS_STATUS_TRYAGAIN : NSS_STATUS_NOTFOUND;
++  if (canon != NULL)
++    {
++      *h_errnop = HOST_NOT_FOUND;
++      return NSS_STATUS_NOTFOUND;
++    }
++
++  *h_errnop = NETDB_INTERNAL;
++  return NSS_STATUS_TRYAGAIN;
+ }
+ 
+ 
+@@ -1242,8 +1252,15 @@ gaih_getanswer (const querybuf *answer1, int anslen1, const querybuf *answer2,
+ 						     &pat, &buffer, &buflen,
+ 						     errnop, h_errnop, ttlp,
+ 						     &first);
++      /* Use the second response status in some cases.  */
+       if (status != NSS_STATUS_SUCCESS && status2 != NSS_STATUS_NOTFOUND)
+ 	status = status2;
++      /* Do not return a truncated second response (unless it was
++         unavoidable e.g. unrecoverable TRYAGAIN).  */
++      if (status == NSS_STATUS_SUCCESS
++	  && (status2 == NSS_STATUS_TRYAGAIN
++	      && *errnop == ERANGE && *h_errnop != NO_RECOVERY))
++	status = NSS_STATUS_TRYAGAIN;
+     }
+ 
+   return status;
+--- a/resolv/res_query.c
++++ b/resolv/res_query.c
+@@ -396,6 +396,7 @@ __libc_res_nsearch(res_state statp,
+ 		  {
+ 		    free (*answerp2);
+ 		    *answerp2 = NULL;
++		    *nanswerp2 = 0;
+ 		    *answerp2_malloced = 0;
+ 		  }
+ 	}
+@@ -447,6 +448,7 @@ __libc_res_nsearch(res_state statp,
+ 			  {
+ 			    free (*answerp2);
+ 			    *answerp2 = NULL;
++			    *nanswerp2 = 0;
+ 			    *answerp2_malloced = 0;
+ 			  }
+ 
+@@ -521,6 +523,7 @@ __libc_res_nsearch(res_state statp,
+ 	  {
+ 	    free (*answerp2);
+ 	    *answerp2 = NULL;
++	    *nanswerp2 = 0;
+ 	    *answerp2_malloced = 0;
+ 	  }
+ 	if (saved_herrno != -1)
+--- a/resolv/res_send.c
++++ b/resolv/res_send.c
+@@ -639,11 +639,7 @@ send_vc(res_state statp,
+ {
+ 	const HEADER *hp = (HEADER *) buf;
+ 	const HEADER *hp2 = (HEADER *) buf2;
+-	u_char *ans = *ansp;
+-	int orig_anssizp = *anssizp;
+-	// XXX REMOVE
+-	// int anssiz = *anssizp;
+-	HEADER *anhp = (HEADER *) ans;
++	HEADER *anhp = (HEADER *) *ansp;
+ 	struct sockaddr *nsap = get_nsaddr (statp, ns);
+ 	int truncating, connreset, n;
+ 	/* On some architectures compiler might emit a warning indicating
+@@ -767,35 +763,6 @@ send_vc(res_state statp,
+ 		assert (anscp != NULL || ansp2 == NULL);
+ 		thisresplenp = &resplen;
+ 	} else {
+-		if (*anssizp != MAXPACKET) {
+-			/* No buffer allocated for the first
+-			   reply.  We can try to use the rest
+-			   of the user-provided buffer.  */
+-#if __GNUC_PREREQ (4, 7)
+-			DIAG_PUSH_NEEDS_COMMENT;
+-			DIAG_IGNORE_NEEDS_COMMENT (5, "-Wmaybe-uninitialized");
+-#endif
+-#if _STRING_ARCH_unaligned
+-			*anssizp2 = orig_anssizp - resplen;
+-			*ansp2 = *ansp + resplen;
+-#else
+-			int aligned_resplen
+-			  = ((resplen + __alignof__ (HEADER) - 1)
+-			     & ~(__alignof__ (HEADER) - 1));
+-			*anssizp2 = orig_anssizp - aligned_resplen;
+-			*ansp2 = *ansp + aligned_resplen;
+-#endif
+-#if __GNUC_PREREQ (4, 7)
+-			DIAG_POP_NEEDS_COMMENT;
+-#endif
+-		} else {
+-			/* The first reply did not fit into the
+-			   user-provided buffer.  Maybe the second
+-			   answer will.  */
+-			*anssizp2 = orig_anssizp;
+-			*ansp2 = *ansp;
+-		}
+-
+ 		thisanssizp = anssizp2;
+ 		thisansp = ansp2;
+ 		thisresplenp = resplen2;
+@@ -804,10 +771,14 @@ send_vc(res_state statp,
+ 	anhp = (HEADER *) *thisansp;
+ 
+ 	*thisresplenp = rlen;
+-	if (rlen > *thisanssizp) {
+-		/* Yes, we test ANSCP here.  If we have two buffers
+-		   both will be allocatable.  */
+-		if (__glibc_likely (anscp != NULL))       {
++	/* Is the answer buffer too small?  */
++	if (*thisanssizp < rlen) {
++		/* If the current buffer is not the the static
++		   user-supplied buffer then we can reallocate
++		   it.  */
++		if (thisansp != NULL && thisansp != ansp) {
++			/* Always allocate MAXPACKET, callers expect
++			   this specific size.  */
+ 			u_char *newp = malloc (MAXPACKET);
+ 			if (newp == NULL) {
+ 				*terrno = ENOMEM;
+@@ -957,8 +928,6 @@ send_dg(res_state statp,
+ {
+ 	const HEADER *hp = (HEADER *) buf;
+ 	const HEADER *hp2 = (HEADER *) buf2;
+-	u_char *ans = *ansp;
+-	int orig_anssizp = *anssizp;
+ 	struct timespec now, timeout, finish;
+ 	struct pollfd pfd[1];
+ 	int ptimeout;
+@@ -1154,50 +1123,48 @@ send_dg(res_state statp,
+ 			assert (anscp != NULL || ansp2 == NULL);
+ 			thisresplenp = &resplen;
+ 		} else {
+-			if (*anssizp != MAXPACKET) {
+-				/* No buffer allocated for the first
+-				   reply.  We can try to use the rest
+-				   of the user-provided buffer.  */
+-#if _STRING_ARCH_unaligned
+-				*anssizp2 = orig_anssizp - resplen;
+-				*ansp2 = *ansp + resplen;
+-#else
+-				int aligned_resplen
+-				  = ((resplen + __alignof__ (HEADER) - 1)
+-				     & ~(__alignof__ (HEADER) - 1));
+-				*anssizp2 = orig_anssizp - aligned_resplen;
+-				*ansp2 = *ansp + aligned_resplen;
+-#endif
+-			} else {
+-				/* The first reply did not fit into the
+-				   user-provided buffer.  Maybe the second
+-				   answer will.  */
+-				*anssizp2 = orig_anssizp;
+-				*ansp2 = *ansp;
+-			}
+-
+ 			thisanssizp = anssizp2;
+ 			thisansp = ansp2;
+ 			thisresplenp = resplen2;
+ 		}
+ 
+ 		if (*thisanssizp < MAXPACKET
+-		    /* Yes, we test ANSCP here.  If we have two buffers
+-		       both will be allocatable.  */
+-		    && anscp
++		    /* If the current buffer is not the the static
++		       user-supplied buffer then we can reallocate
++		       it.  */
++		    && (thisansp != NULL && thisansp != ansp)
+ #ifdef FIONREAD
++		    /* Is the size too small?  */
+ 		    && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0
+ 			|| *thisanssizp < *thisresplenp)
+ #endif
+                     ) {
++			/* Always allocate MAXPACKET, callers expect
++			   this specific size.  */
+ 			u_char *newp = malloc (MAXPACKET);
+ 			if (newp != NULL) {
+-				*anssizp = MAXPACKET;
+-				*thisansp = ans = newp;
++				*thisanssizp = MAXPACKET;
++				*thisansp = newp;
+ 				if (thisansp == ansp2)
+ 				  *ansp2_malloced = 1;
+ 			}
+ 		}
++		/* We could end up with truncation if anscp was NULL
++		   (not allowed to change caller's buffer) and the
++		   response buffer size is too small.  This isn't a
++		   reliable way to detect truncation because the ioctl
++		   may be an inaccurate report of the UDP message size.
++		   Therefore we use this only to issue debug output.
++		   To do truncation accurately with UDP we need
++		   MSG_TRUNC which is only available on Linux.  We
++		   can abstract out the Linux-specific feature in the
++		   future to detect truncation.  */
++		if (__glibc_unlikely (*thisanssizp < *thisresplenp)) {
++			Dprint(statp->options & RES_DEBUG,
++			       (stdout, ";; response may be truncated (UDP)\n")
++			);
++		}
++
+ 		HEADER *anhp = (HEADER *) *thisansp;
+ 		socklen_t fromlen = sizeof(struct sockaddr_in6);
+ 		assert (sizeof(from) <= fromlen);