getmntent: fix memory corruption w/blank lines [BZ #18887]

The fix for BZ #17273 introduced a single byte of memory corruption when
the line is entirely blank.  It would walk back past the start of the
buffer if the heap happened to be 0x20 or 0x09 and then write a NUL byte.
	buffer = '\n';
	end_ptr = buffer;
	while (end_ptr[-1] == ' ' || end_ptr[-1] == '\t')
		end_ptr--;
	*end_ptr = '\0';

Fix that and rework the tests.  Adding the testcase for BZ #17273 to the
existing \040 parser does not really make sense as it's unrelated, and
leads to confusing behavior: it implicitly relies on the new entry being
longer than the previous entry (since it just rewinds the FILE*).  Split
it out into its own dedicated testcase instead.

diff --git a/ChangeLog b/ChangeLog
index 96e01f09091eeaaa4610cde7aa2081e2bc875c1c..99129d39a5684c41255897607f65075b30754a4b 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2015-08-28  Mike Frysinger  <vapier@gentoo.org>
+
+       [BZ #18887]
+       * misc/Makefile (tests): Add tst-mntent-blank-corrupt and
+       tst-mntent-blank-passno.
+       * misc/mntent_r.c (__getmntent_r): Do not read past buffer[0].
+       * misc/tst-mntent-blank-corrupt.c: New test.
+       * misc/tst-mntent-blank-passno.c: New test ripped from ...
+       * misc/tst-mntent.c (do_test): ... here.
+
 2015-08-29  Mike Frysinger  <vapier@gentoo.org>
 
        [BZ #4404]

diff --git a/misc/Makefile b/misc/Makefile
index aecb0dae9db3cfa352acd2c8b4b8c864fb1bc9c6..2f5edf6316dacc282def12ed3363432b974bc485 100644 (file)
--- 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 \
+        tst-mntent-blank-corrupt tst-mntent-blank-passno
 ifeq ($(run-built-tests),yes)
 tests-special += $(objpfx)tst-error1-mem.out
 endif

diff --git a/misc/mntent_r.c b/misc/mntent_r.c
index 615987347abc9845aef0a8a4da3e392072adff8e..4f269984d70a8734f043c03d6f2afb3e62d9f785 100644 (file)
--- a/misc/mntent_r.c
+++ b/misc/mntent_r.c
@@ -136,7 +136,9 @@ __getmntent_r (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
       end_ptr = strchr (buffer, '\n');
       if (end_ptr != NULL)     /* chop newline */
        {
-         while (end_ptr[-1] == ' ' || end_ptr[-1] == '\t')
+         /* Do not walk past the start of buffer if it's all whitespace.  */
+         while (end_ptr != buffer
+                && (end_ptr[-1] == ' ' || end_ptr[-1] == '\t'))
             end_ptr--;
          *end_ptr = '\0';
        }

diff --git a/misc/tst-mntent-blank-corrupt.c b/misc/tst-mntent-blank-corrupt.c
new file mode 100644 (file)
index 0000000..92266a3
--- /dev/null
+++ b/misc/tst-mntent-blank-corrupt.c
@@ -0,0 +1,45 @@
+/* Make sure blank lines does not cause memory corruption BZ #18887.
+
+   Copyright (C) 2009-2015 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 <mntent.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Make sure blank lines don't trigger memory corruption.  This doesn't happen
+   for all targets though, so it's a best effort test BZ #18887.  */
+static int
+do_test (void)
+{
+  FILE *fp;
+
+  fp = tmpfile ();
+  fputs ("\n \n/foo\\040dir /bar\\040dir auto bind \t \n", fp);
+  rewind (fp);
+
+  /* The corruption happens here ...  */
+  getmntent (fp);
+  /* ... but trigers here.  */
+  endmntent (fp);
+
+  /* If the test failed, we would crash, and not hit this point.  */
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"

diff --git a/misc/tst-mntent-blank-passno.c b/misc/tst-mntent-blank-passno.c
new file mode 100644 (file)
index 0000000..fc04291
--- /dev/null
+++ b/misc/tst-mntent-blank-passno.c
@@ -0,0 +1,53 @@
+/* Make sure trailing whitespace is handled properly BZ #17273.
+
+   Copyright (C) 2009-2015 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 <mntent.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Check entries to make sure trailing whitespace is ignored and we return the
+   correct passno value BZ #17273.  */
+static int
+do_test (void)
+{
+  int result = 0;
+  FILE *fp;
+  struct mntent *mnt;
+
+  fp = tmpfile ();
+  fputs ("/foo\\040dir /bar\\040dir auto bind \t \n", fp);
+  rewind (fp);
+
+  mnt = getmntent (fp);
+  if (strcmp (mnt->mnt_fsname, "/foo dir") != 0
+      || strcmp (mnt->mnt_dir, "/bar dir") != 0
+      || strcmp (mnt->mnt_type, "auto") != 0
+      || strcmp (mnt->mnt_opts, "bind") != 0
+      || mnt->mnt_freq != 0
+      || mnt->mnt_passno != 0)
+    {
+      puts ("Error while reading entry with trailing whitespaces");
+      result = 1;
+    }
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"

diff --git a/misc/tst-mntent.c b/misc/tst-mntent.c
index 932fd3f522a300d73fd1af8641b02800a21c1fad..b6ad8afcc6ee644cc57544f5d0c3461188b1d033 100644 (file)
--- a/misc/tst-mntent.c
+++ b/misc/tst-mntent.c
@@ -73,26 +73,6 @@ do_test (void)
          puts ("Error while reading written entry back in");
          result = 1;
        }
-
-      /* Part III: Entry with whitespaces at the end of a line. */
-      rewind (fp);
-
-      fputs ("/foo\\040dir /bar\\040dir auto bind \t \n", fp);
-
-      rewind (fp);
-
-      mnt = getmntent (fp);
-
-      if (strcmp (mnt->mnt_fsname, "/foo dir") != 0
-         || strcmp (mnt->mnt_dir, "/bar dir") != 0
-         || strcmp (mnt->mnt_type, "auto") != 0
-         || strcmp (mnt->mnt_opts, "bind") != 0
-         || mnt->mnt_freq != 0
-         || mnt->mnt_passno != 0)
-       {
-         puts ("Error while reading entry with trailing whitespaces");
-         result = 1;
-       }
    }
 
   return result;