[PATCH] Fix buffer overrun in regexp matcher

[Andreas Schwab]

When extending regex buffers, make sure we allocate enough room for the
state log.  Merely doubling the space may not be enough if the current
node has accepted a long run of characters.  This part of the code only
triggers with multibyte characters.

Andreas.

	[BZ #15078]
	* posix/regexec.c (extend_buffers): Add parameter min_len.
	(check_matching): Pass minimum needed length.
	(clean_state_log_if_needed): Likewise.
	(get_subexp): Likewise.
	* posix/Makefile (tests): Add bug-regex34.
	(bug-regex34-ENV): Define.
	* posix/bug-regex34.c: New file.

diff --git a/NEWS b/NEWS
index 9a039d8..ec4175c 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.18
 * The following bugs are resolved with this release:
 
   13951, 14200, 14317, 14327, 14496, 14964, 14981, 14982, 14985, 14994,
-  14996, 15003, 15020, 15023, 15036.
+  14996, 15003, 15020, 15023, 15036, 15078.
 
 

 Version 2.17
diff --git a/posix/Makefile b/posix/Makefile
index 57672d8..6ceb440 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -86,7 +86,7 @@ tests		:= tstgetopt testfnm runtests runptests	     \
 		   tst-rfc3484-3 \
 		   tst-getaddrinfo3 tst-fnmatch2 tst-cpucount tst-cpuset \
 		   bug-getopt1 bug-getopt2 bug-getopt3 bug-getopt4 \
-		   bug-getopt5 tst-getopt_long1
+		   bug-getopt5 tst-getopt_long1 bug-regex34
 xtests		:= bug-ga2
 ifeq (yes,$(build-shared))
 test-srcs	:= globtest
@@ -199,6 +199,7 @@ bug-regex26-ENV = LOCPATH=$(common-objpfx)localedata
 bug-regex30-ENV = LOCPATH=$(common-objpfx)localedata
 bug-regex32-ENV = LOCPATH=$(common-objpfx)localedata
 bug-regex33-ENV = LOCPATH=$(common-objpfx)localedata
+bug-regex34-ENV = LOCPATH=$(common-objpfx)localedata
 tst-rxspencer-ARGS = --utf8 rxspencer/tests
 tst-rxspencer-ENV = LOCPATH=$(common-objpfx)localedata
 tst-pcre-ARGS = PCRE.tests
diff --git a/posix/bug-regex34.c b/posix/bug-regex34.c
new file mode 100644
index 0000000..bb3b613
--- /dev/null
+++ b/posix/bug-regex34.c
@@ -0,0 +1,46 @@
+/* Test re_search with multi-byte characters in UTF-8.
+   Copyright (C) 2013 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/>.  */
+
+#define _GNU_SOURCE 1
+#include <stdio.h>
+#include <string.h>
+#include <locale.h>
+#include <regex.h>
+
+static int
+do_test (void)
+{
+  struct re_pattern_buffer r;
+  /* ကျွန်ုပ်x */
+  const char *s = "\xe1\x80\x80\xe1\x80\xbb\xe1\x80\xbd\xe1\x80\x94\xe1\x80\xba\xe1\x80\xaf\xe1\x80\x95\xe1\x80\xbax";
+
+  if (setlocale (LC_ALL, "en_US.UTF-8") == NULL)
+    {
+      puts ("setlocale failed");
+      return 1;
+    }
+  memset (&r, 0, sizeof (r));
+
+  re_compile_pattern ("[^x]x", 5, &r);
+  /* This was triggering a buffer overflow.  */
+  re_search (&r, s, strlen (s), 0, strlen (s), 0);
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/posix/regexec.c b/posix/regexec.c
index 7f2de85..5ca2bf6 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -197,7 +197,7 @@ static int group_nodes_into_DFAstates (const re_dfa_t *dfa,
 static int check_node_accept (const re_match_context_t *mctx,
 			      const re_token_t *node, int idx)
      internal_function;
-static reg_errcode_t extend_buffers (re_match_context_t *mctx)
+static reg_errcode_t extend_buffers (re_match_context_t *mctx, int min_len)
      internal_function;
 

 /* Entry point for POSIX code.  */
@@ -1160,7 +1160,7 @@ check_matching (re_match_context_t *mctx, int fl_longest_match,
 	  || (BE (next_char_idx >= mctx->input.valid_len, 0)
 	      && mctx->input.valid_len < mctx->input.len))
 	{
-	  err = extend_buffers (mctx);
+	  err = extend_buffers (mctx, next_char_idx + 1);
 	  if (BE (err != REG_NOERROR, 0))
 	    {
 	      assert (err == REG_ESPACE);
@@ -1738,7 +1738,7 @@ clean_state_log_if_needed (re_match_context_t *mctx, int next_state_log_idx)
 	  && mctx->input.valid_len < mctx->input.len))
     {
       reg_errcode_t err;
-      err = extend_buffers (mctx);
+      err = extend_buffers (mctx, next_state_log_idx + 1);
       if (BE (err != REG_NOERROR, 0))
 	return err;
     }
@@ -2792,7 +2792,7 @@ get_subexp (re_match_context_t *mctx, int bkref_node, int bkref_str_idx)
 		  if (bkref_str_off >= mctx->input.len)
 		    break;
 
-		  err = extend_buffers (mctx);
+		  err = extend_buffers (mctx, bkref_str_off + 1);
 		  if (BE (err != REG_NOERROR, 0))
 		    return err;
 
@@ -4102,7 +4102,7 @@ check_node_accept (const re_match_context_t *mctx, const re_token_t *node,
 
 static reg_errcode_t
 internal_function __attribute_warn_unused_result__
-extend_buffers (re_match_context_t *mctx)
+extend_buffers (re_match_context_t *mctx, int min_len)
 {
   reg_errcode_t ret;
   re_string_t *pstr = &mctx->input;
@@ -4111,8 +4111,10 @@ extend_buffers (re_match_context_t *mctx)
   if (BE (INT_MAX / 2 / sizeof (re_dfastate_t *) <= pstr->bufs_len, 0))
     return REG_ESPACE;
 
-  /* Double the lengthes of the buffers.  */
-  ret = re_string_realloc_buffers (pstr, MIN (pstr->len, pstr->bufs_len * 2));
+  /* Double the lengthes of the buffers, but allocate at least MIN_LEN.  */
+  ret = re_string_realloc_buffers (pstr,
+				   MAX (min_len,
+					MIN (pstr->len, pstr->bufs_len * 2)));
   if (BE (ret != REG_NOERROR, 0))
     return ret;
 
-- 
1.8.1.2


-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."