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

(cherry picked from commit bae7c7c764413b23e61cb099ce33be4c4ee259bb)

4 files changed, 106 insertions, 19 deletions

diff --git a/ChangeLog b/ChangeLog
index 64dea2e8f1..cd343c7090 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2016-05-24  Paul Eggert  <eggert@cs.ucla.edu>
+
+	[BZ #18240]
+	* misc/hsearch_r.c (isprime, __hcreate_r): Protect against
+	unsigned int wraparound.
+
+2016-05-24  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #18240]
+	* misc/bug18240.c: New test.
+	* misc/Makefile (tests): Add it.
+
 2016-05-24  Ondřej Bílka  <neleai@seznam.cz>
 
 	* debug/strcpy_chk.c: Improve performance.
diff --git a/misc/Makefile b/misc/Makefile
index edac24cfc2..ec5f9616f6 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -76,7 +76,8 @@ install-lib := libg.a
 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-error1 tst-pselect tst-insremque tst-mntent2 bug-hsearch1 \
+	 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 0000000000..4b26865a31
--- /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 4414a25cba..af5521234c 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;