hcreate, hcreate_r should fail with ENOMEM if element count is too large (BZ18240, CVE-2015-8778)

README.google

@@ -641,3 +641,11 @@ sysdeps/generic/ldsodefs.h
   Always enable pointer guard (BZ18928, CVE-2015-8777)
   https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a014cecd82b71b70a6a843e250e06b541ad524f7
   (stanshebs, backport)
+
+misc/Makefile
+misc/bug18240.c
+misc/hsearch_r.c
+  hcreate, hcreate_r should fail with ENOMEM if element count is too large (BZ18240, CVE-2015-8778)
+  https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b5cba5cff937e5336ff23380785da80cab09146c
+  https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3c9e8d9477aba0f514171bb4706670052544479b
+  (stanshebs, backport)

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: $(objpfx)tst-error1-mem
 endif

misc/bug18240.c

@@ -0,0 +1,97 @@
+/* Test integer wraparound in hcreate.
+   Copyright (C) 2016-2017 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>
+#include <sys/resource.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)
+{
+  /* Limit the size of the process, so that memory allocation will
+     fail without impacting the entire system.  */
+  {
+    struct rlimit limit;
+    if (getrlimit (RLIMIT_AS, &limit) != 0)
+      {
+        printf ("getrlimit (RLIMIT_AS) failed: %m\n");
+        return 1;
+      }
+    long target = 100 * 1024 * 1024;
+    if (limit.rlim_cur == RLIM_INFINITY || limit.rlim_cur > target)
+      {
+        limit.rlim_cur = target;
+        if (setrlimit (RLIMIT_AS, &limit) != 0)
+          {
+            printf ("setrlimit (RLIMIT_AS) failed: %m\n");
+            return 1;
+          }
+      }
+  }
+
+  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"

misc/hsearch_r.c

@@ -19,7 +19,7 @@
 #include <errno.h>
 #include <malloc.h>
 #include <string.h>
-
+#include <stdint.h>
 #include <search.h>
 
 /* [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
@@ -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
@@ -81,10 +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;