Re: [PATCH v6] io: Fix ftw internal realloc buffer (BZ #28126)

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

Ping.

On 27/09/2021 12:26, Adhemerval Zanella wrote:
> The 106ff08526d3ca did not take in consideration the buffer might be
> reallocated if the total path is larger than PATH_MAX.  The realloc
> uses 'dirbuf', where 'dirstreams' is the allocated buffer.
> 
> Checked on x86_64-linux-gnu.
> ---
>  io/Makefile          |  1 +
>  io/ftw.c             | 13 +++---
>  io/tst-ftw-bz28126.c | 97 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 106 insertions(+), 5 deletions(-)
>  create mode 100644 io/tst-ftw-bz28126.c
> 
> diff --git a/io/Makefile b/io/Makefile
> index 9871ecbc74..ecf65aba60 100644
> --- a/io/Makefile
> +++ b/io/Makefile
> @@ -79,6 +79,7 @@ tests		:= test-utime test-stat test-stat2 test-lfs tst-getcwd \
>  		   tst-futimens \
>  		   tst-utimensat \
>  		   tst-closefrom \
> +		   tst-ftw-bz28126
>  
>  tests-time64 := \
>    tst-futimens-time64 \
> diff --git a/io/ftw.c b/io/ftw.c
> index f0db173727..3964c07bbb 100644
> --- a/io/ftw.c
> +++ b/io/ftw.c
> @@ -391,13 +391,16 @@ process_entry (struct ftw_data *data, struct dir_data *dir, const char *name,
>    if (data->dirbufsize < new_buflen)
>      {
>        /* Enlarge the buffer.  */
> -      char *newp;
> -
> -      data->dirbufsize = 2 * new_buflen;
> -      newp = (char *) realloc (data->dirbuf, data->dirbufsize);
> +      size_t newsize = 2 * new_buflen;
> +      void *newp = realloc (data->dirstreams, data->maxdir
> +					      * sizeof (struct dir_data *)
> +					      + newsize);
>        if (newp == NULL)
>  	return -1;
> -      data->dirbuf = newp;
> +      data->dirstreams = newp;
> +      data->dirbufsize = newsize;
> +      data->dirbuf = (char *) data->dirstreams
> +		     + data->maxdir * sizeof (struct dir_data *);
>      }
>  
>    *((char *) __mempcpy (data->dirbuf + data->ftw.base, name, namlen)) = '\0';
> diff --git a/io/tst-ftw-bz28126.c b/io/tst-ftw-bz28126.c
> new file mode 100644
> index 0000000000..94044ab9d1
> --- /dev/null
> +++ b/io/tst-ftw-bz28126.c
> @@ -0,0 +1,97 @@
> +/* Check if internal buffer reallocation work for large paths (BZ #28126)
> +   Copyright (C) 2021 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
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <errno.h>
> +#include <ftw.h>
> +#include <limits.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/temp_file.h>
> +#include <support/xunistd.h>
> +#include <stdio.h>
> +
> +static int
> +my_func (const char *file, const struct stat *sb, int flag)
> +{
> +  return 0;
> +}
> +
> +static const char folder[NAME_MAX] = { [0 ... 253] = 'a', [254] = '\0' };
> +
> +#define NSUBFOLDERS 16
> +static int nsubfolders;
> +
> +static void
> +do_cleanup (void)
> +{
> +  xchdir ("..");
> +  for (int i = 0; i < nsubfolders; i++)
> +    {
> +      remove (folder);
> +      xchdir ("..");
> +    }
> +  remove (folder);
> +}
> +#define CLEANUP_HANDLER do_cleanup
> +
> +static void
> +check_mkdir (const char *path)
> +{
> +  int r = mkdir (path, 0777);
> +  /* Some filesystem such as overlayfs does not support larger path required
> +     to trigger the internal buffer reallocation.  */
> +  if (r != 0)
> +    {
> +      if (errno == ENAMETOOLONG)
> +	FAIL_UNSUPPORTED ("the filesystem does not support the required"
> +			  "large path");
> +      else
> +	FAIL_EXIT1 ("mkdir (\"%s\", 0%o): %m", folder, 0777);
> +    }
> +}
> +
> +static int
> +do_test (void)
> +{
> +  char *tempdir = support_create_temp_directory ("tst-bz28126");
> +
> +  /* Create path with various subfolders to force an internal buffer
> +     reallocation within ntfw.  */
> +  char *path = xasprintf ("%s/%s", tempdir, folder);
> +  check_mkdir (path);
> +  xchdir (path);
> +  free (path);
> +  for (int i = 0; i < NSUBFOLDERS - 1; i++)
> +    {
> +      check_mkdir (folder);
> +      xchdir (folder);
> +      nsubfolders++;
> +    }
> +
> +  TEST_COMPARE (ftw (tempdir, my_func, 20), 0);
> +
> +  free (tempdir);
> +
> +  do_cleanup ();
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
>