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[PATCH] Improve check against integer wraparound in hcreate_r [BZ #18240]


It turns out that the previous check did not actually fix the bug.

If we do not include this additional change in the upcoming release, for
consistency's sake, we'd have to allocate another CVE ID.

Florian
2016-01-22  Florian Weimer  <fweimer@redhat.com>

	[BZ #18240]
	* misc/hsearch_r.c (__hcreate_r): Protect against unsigned int
	wraparound.
	* misc/bug18240.c: New test.
	* misc/Makefile (tests): Add it.

diff --git a/misc/Makefile b/misc/Makefile
index b9f854e..d7bbc85 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -77,7 +77,7 @@ gpl2lgpl := error.c error.h
 
 tests := tst-dirname tst-tsearch tst-fdset tst-efgcvt tst-mntent tst-hsearch \
 	 tst-error1 tst-pselect tst-insremque tst-mntent2 bug-hsearch1 \
-	 tst-mntent-blank-corrupt tst-mntent-blank-passno
+	 tst-mntent-blank-corrupt tst-mntent-blank-passno bug18240
 ifeq ($(run-built-tests),yes)
 tests-special += $(objpfx)tst-error1-mem.out
 endif
diff --git a/misc/bug18240.c b/misc/bug18240.c
new file mode 100644
index 0000000..1223486
--- /dev/null
+++ b/misc/bug18240.c
@@ -0,0 +1,69 @@
+/* Test integer wraparound in hcreate.
+   Copyright (C) 2016 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 <errno.h>
+#include <limits.h>
+#include <search.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static void
+test_size (size_t size)
+{
+  int res = hcreate (size);
+  if (res == 0)
+    {
+      if (errno == ENOMEM)
+        return;
+      printf ("error: hcreate (%zu): %m\n", size);
+      exit (1);
+    }
+  char *keys[100];
+  for (int i = 0; i < 100; ++i)
+    {
+      if (asprintf (keys + i, "%d", i) < 0)
+        {
+          printf ("error: asprintf: %m\n");
+          exit (1);
+        }
+      ENTRY e = { keys[i], (char *) "value" };
+      if (hsearch (e, ENTER) == NULL)
+        {
+          printf ("error: hsearch (\"%s\"): %m\n", keys[i]);
+          exit (1);
+        }
+    }
+  hdestroy ();
+
+  for (int i = 0; i < 100; ++i)
+    free (keys[i]);
+}
+
+static int
+do_test (void)
+{
+  test_size (-1);
+  test_size (-3);
+  test_size (INT_MAX);
+  test_size (UINT_MAX);
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/misc/hsearch_r.c b/misc/hsearch_r.c
index f6f16ed..8955d85 100644
--- a/misc/hsearch_r.c
+++ b/misc/hsearch_r.c
@@ -71,7 +71,10 @@ __hcreate_r (size_t nel, struct hsearch_data *htab)
       return 0;
     }
 
-  if (nel >= SIZE_MAX / sizeof (_ENTRY))
+  /* This limit is sufficient to avoid unsigned wraparound below,
+     possibly after truncation to unsigned int.  (struct hsearch_data
+     is part of the public API and uses usigned ints.)  */
+  if (nel >= INT_MAX / sizeof (_ENTRY))
     {
       __set_errno (ENOMEM);
       return 0;

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