[COMMITTED 2.21] Improve check against integer wraparound in hcreate_r [BZ #18240]

[Aurelien Jarno]

From: Florian Weimer <fweimer@redhat.com>

(cherry picked from commit bae7c7c764413b23e61cb099ce33be4c4ee259bb)
---
 ChangeLog        | 12 +++++++++
 NEWS             |  2 +-
 misc/Makefile    |  2 +-
 misc/bug18240.c  | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 misc/hsearch_r.c | 35 +++++++++++++-------------
 5 files changed, 106 insertions(+), 20 deletions(-)
 create mode 100644 misc/bug18240.c

diff --git a/ChangeLog b/ChangeLog
index 9fb7fd6..a38da43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2016-01-27  Paul Eggert  <eggert@cs.ucla.edu>
+
+	[BZ #18240]
+	* misc/hsearch_r.c (isprime, __hcreate_r): Protect against
+	unsigned int wraparound.
+
+2016-01-27  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #18240]
+	* misc/bug18240.c: New test.
+	* misc/Makefile (tests): Add it.
+
 2015-08-25  Ondřej Bílka  <neleai@seznam.cz>
 
 	[BZ #18240]
diff --git a/NEWS b/NEWS
index e659b75..40f8c90 100644
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,7 @@ Version 2.21.1
 
 * The following bugs are resolved with this release:
 
-  17269, 17905, 17949, 18007, 18032, 18287, 18694, 18887, 18985.
+  17269, 17905, 17949, 18007, 18032, 18240, 18287, 18694, 18887, 18985.
 
 * A buffer overflow in gethostbyname_r and related functions performing DNS
   requests has been fixed.  If the NSS functions were called with a
diff --git a/misc/Makefile b/misc/Makefile
index 2f5edf6..12055ce 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..4b26865
--- /dev/null
+++ b/misc/bug18240.c
@@ -0,0 +1,75 @@
+/* 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 (500);
+  test_size (-1);
+  test_size (-3);
+  test_size (INT_MAX - 2);
+  test_size (INT_MAX - 1);
+  test_size (INT_MAX);
+  test_size (((unsigned) INT_MAX) + 1);
+  test_size (UINT_MAX - 2);
+  test_size (UINT_MAX - 1);
+  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 8b368cb..91fa63f 100644
--- a/misc/hsearch_r.c
+++ b/misc/hsearch_r.c
@@ -46,15 +46,12 @@ static int
 isprime (unsigned int number)
 {
   /* no even number will be passed */
-  unsigned int div = 3;
-
-  while (div * div < number && number % div != 0)
-    div += 2;
-
-  return number % div != 0;
+  for (unsigned int div = 3; div <= number / div; div += 2)
+    if (number % div == 0)
+      return 0;
+  return 1;
 }
 
-
 /* Before using the hash table we must allocate memory for it.
    Test for an existing table are done. We allocate one element
    more as the found prime number says. This is done for more effective
@@ -73,13 +70,6 @@ hcreate_r (nel, htab)
       return 0;
     }
 
-  if (nel >= SIZE_MAX / sizeof (_ENTRY))
-    {
-      __set_errno (ENOMEM);
-      return 0;
-    }
-
-
   /* There is still another table active. Return with error. */
   if (htab->table != NULL)
     return 0;
@@ -88,10 +78,19 @@ hcreate_r (nel, htab)
      use will not work.  */
   if (nel < 3)
     nel = 3;
-  /* Change nel to the first prime number not smaller as nel. */
-  nel |= 1;      /* make odd */
-  while (!isprime (nel))
-    nel += 2;
+
+  /* Change nel to the first prime number in the range [nel, UINT_MAX - 2],
+     The '- 2' means 'nel += 2' cannot overflow.  */
+  for (nel |= 1; ; nel += 2)
+    {
+      if (UINT_MAX - 2 < nel)
+	{
+	  __set_errno (ENOMEM);
+	  return 0;
+	}
+      if (isprime (nel))
+	break;
+    }
 
   htab->size = nel;
   htab->filled = 0;
-- 
2.7.0.rc3