Fix path length overflow in realpath (BZ#22786)
Commit Message
On Tue, Apr 10, 2018 at 8:15 AM Andreas Schwab <schwab@suse.de> wrote:
> On Apr 10 2018, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:
> > Should I change the test to pass if allocation fails?
> No, unsupported.
Right. Revised patch attached.
--
Paul Pluzhnikov
@@ -84,7 +84,7 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
tst-cxa_atexit tst-on_exit test-atexit-race \
test-at_quick_exit-race test-cxa_atexit-race \
test-on_exit-race test-dlclose-exit-race \
- tst-makecontext-align
+ tst-makecontext-align test-bz22786
tests-internal := tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \
tst-tls-atexit tst-tls-atexit-nodelete
@@ -156,6 +156,9 @@ CFLAGS-tst-qsort.c += $(stack-align-test-flags)
CFLAGS-tst-makecontext.c += -funwind-tables
CFLAGS-tst-makecontext2.c += $(stack-align-test-flags)
+# suppress warnings about allocation size.
+CFLAGS-test-bz22786.c += $(+gcc-nowarn)
+
# Run a test on the header files we use.
tests-special += $(objpfx)isomac.out
@@ -181,7 +181,7 @@ __realpath (const char *name, char *resolved)
extra_buf = __alloca (path_max);
len = strlen (end);
- if ((long int) (n + len) >= path_max)
+ if (path_max - n <= len)
{
__set_errno (ENAMETOOLONG);
goto error;
new file mode 100644
@@ -0,0 +1,81 @@
+/* Bug 22786: test for stack overflow in realpath.
+ Copyright (C) 2018 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/>. */
+
+/* This file must be run from within a directory called "stdlib". */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <support/test-driver.h>
+
+static int
+do_test (void)
+{
+ const char dir[] = "bz22786";
+ const char lnk[] = "bz22786/symlink";
+
+ rmdir (dir);
+ if (mkdir (dir, 0755) != 0 && errno != EEXIST)
+ {
+ printf ("mkdir %s: %m\n", dir);
+ return EXIT_FAILURE;
+ }
+ if (symlink (".", lnk) != 0 && errno != EEXIST)
+ {
+ printf ("symlink (%s, %s): %m\n", dir, lnk);
+ return EXIT_FAILURE;
+ }
+
+ const size_t path_len = (size_t) INT_MAX + 1;
+ char *path = malloc (path_len);
+
+ if (path == NULL)
+ {
+ printf ("malloc (%zu): %m\n", path_len);
+ return EXIT_UNSUPPORTED;
+ }
+
+ /* Construct very long path = "bz22786/symlink/aaaa....." */
+ char *p = mempcpy (path, lnk, sizeof (lnk) - 1);
+ *(p++) = '/';
+ memset (p, 'a', path_len - (path - p) - 2);
+ p[path_len - (path - p) - 1] = '\0';
+
+ /* This call crashes before the fix for bz22786 on 32-bit platforms. */
+ p = realpath (path, NULL);
+
+ if (p != NULL || errno != ENAMETOOLONG)
+ {
+ printf ("realpath: %s (%m)", p);
+ return EXIT_FAILURE;
+ }
+
+ /* Cleanup. */
+ unlink (lnk);
+ rmdir (dir);
+
+ return 0;
+}
+
+#define TEST_FUNCTION do_test
+#include <support/test-driver.c>