Re: [PATCH 1/3] support: Add helpers to create paths longer than PATH_MAX

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

On 18/01/2022 06:07, Siddhesh Poyarekar wrote:
> Add new helpers support_create_and_chdir_toolong_temp_directory and
> support_chdir_toolong_temp_directory to create and descend into
> directory trees longer than PATH_MAX.
> 
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
>  support/temp_file.c | 157 +++++++++++++++++++++++++++++++++++++++++---
>  support/temp_file.h |  11 ++++
>  2 files changed, 160 insertions(+), 8 deletions(-)
> 
> diff --git a/support/temp_file.c b/support/temp_file.c
> index e7bb8aadb9..c3e83912ac 100644
> --- a/support/temp_file.c
> +++ b/support/temp_file.c
> @@ -36,14 +36,31 @@ static struct temp_name_list
>    struct temp_name_list *next;
>    char *name;
>    pid_t owner;
> +  bool toolong;
>  } *temp_name_list;
>  
>  /* Location of the temporary files.  Set by the test skeleton via
>     support_set_test_dir.  The string is not be freed.  */
>  static const char *test_dir = _PATH_TMP;
>  
> -void
> -add_temp_file (const char *name)
> +/* Name of subdirectories in a too long temporary directory tree.  */
> +static char toolong_subdir[NAME_MAX + 1];
> +
> +/* Return the maximum size of path on the target.  */
> +static inline size_t
> +get_path_max (void)
> +{
> +#ifdef PATH_MAX
> +  return PATH_MAX;
> +#else
> +  size_t path_max = pathconf ("/", _PC_PATH_MAX);
> +  return (path_max < 0 ? 1024
> +	  : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX);
> +#endif
> +}
> +
> +static void
> +add_temp_file_internal (const char *name, bool toolong)
>  {
>    struct temp_name_list *newp
>      = (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
> @@ -53,12 +70,19 @@ add_temp_file (const char *name)
>        newp->name = newname;
>        newp->next = temp_name_list;
>        newp->owner = getpid ();
> +      newp->toolong = toolong;
>        temp_name_list = newp;
>      }
>    else
>      free (newp);
>  }
>  
> +void
> +add_temp_file (const char *name)
> +{
> +  add_temp_file_internal (name, false);
> +}
> +
>  int
>  create_temp_file_in_dir (const char *base, const char *dir, char **filename)
>  {
> @@ -90,8 +114,8 @@ create_temp_file (const char *base, char **filename)
>    return create_temp_file_in_dir (base, test_dir, filename);
>  }
>  
> -char *
> -support_create_temp_directory (const char *base)
> +static char *
> +create_temp_directory_internal (const char *base, bool toolong)
>  {
>    char *path = xasprintf ("%s/%sXXXXXX", test_dir, base);
>    if (mkdtemp (path) == NULL)
> @@ -99,16 +123,124 @@ support_create_temp_directory (const char *base)
>        printf ("error: mkdtemp (\"%s\"): %m", path);
>        exit (1);
>      }
> -  add_temp_file (path);
> +  add_temp_file_internal (path, toolong);
>    return path;
>  }
>  
> -/* Helper functions called by the test skeleton follow.  */
> +char *
> +support_create_temp_directory (const char *base)
> +{
> +  return create_temp_directory_internal (base, false);
> +}
> +
> +static void
> +ensure_toolong_subdir_initialized (void)
> +{
> +  for (size_t i = 0; i < NAME_MAX; i++)
> +    if (toolong_subdir[i] != 'X')
> +      {
> +	printf ("uninitialized toolong directory tree\n");
> +	exit (1);
> +      }
> +}

Maybe use FAIL_EXIT1 here?

> +
> +char *
> +support_create_and_chdir_toolong_temp_directory (const char *basename)
> +{
> +  size_t path_max = get_path_max ();
> +
> +  char *base = create_temp_directory_internal (basename, true);
> +
> +  if (chdir (base) != 0)
> +    {
> +      printf ("error creating toolong base: chdir (\"%s\"): %m", base);
> +      exit (1);
> +    }
> +

Use xchdir. 

> +  memset (toolong_subdir, 'X', sizeof (toolong_subdir) - 1);
> +  toolong_subdir[NAME_MAX] = '\0';
> +
> +  /* Create directories and descend into them so that the final path is larger
> +     than PATH_MAX.  */
> +  for (size_t i = 0; i <= path_max / sizeof (toolong_subdir); i++)
> +    {
> +      if (mkdir (toolong_subdir, S_IRWXU) != 0)
> +	{
> +	  printf ("error creating toolong subdir: mkdir (\"%s\"): %m",
> +		  toolong_subdir);
> +	  exit (1);
> +	}

Use xmkdir.

> +      if (chdir (toolong_subdir) != 0)


Use xchdir. 

> +	{
> +	  printf ("error creating toolong subdir: chdir (\"%s\"): %m",
> +		  toolong_subdir);
> +	  exit (1);
> +	}
> +    }
> +  return base;
> +}
>  
>  void
> -support_set_test_dir (const char *path)
> +support_chdir_toolong_temp_directory (const char *base)
>  {
> -  test_dir = path;
> +  size_t path_max = get_path_max ();
> +  ensure_toolong_subdir_initialized ();
> +
> +  if (chdir (base) != 0)
> +    {
> +      printf ("error: chdir (\"%s\"): %m", base);
> +      exit (1);
> +    }
> +
> +  for (size_t i = 0; i <= path_max / sizeof (toolong_subdir); i++)
> +    if (chdir (toolong_subdir) != 0)

Use xchdir.

> +      {
> +	printf ("error subdir: chdir (\"%s\"): %m", toolong_subdir);
> +	exit (1);
> +      }
> +}
> +
> +/* Helper functions called by the test skeleton follow.  */
> +
> +static void
> +remove_toolong_subdirs (const char *base)
> +{
> +  size_t path_max = get_path_max ();
> +
> +  ensure_toolong_subdir_initialized ();
> +
> +  if (chdir (base) != 0)
> +    {
> +      printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n",
> +	      base);
> +      return;
> +    }
> +
> +  /* Descend.  */
> +  int levels = 0;
> +  for (levels = 0; levels <= path_max / sizeof (toolong_subdir); levels++)
> +    if (chdir (toolong_subdir) != 0)
> +      {
> +	printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n",
> +		toolong_subdir);
> +	return;
> +      }
> +
> +  /* Ascend and remove.  */
> +  while (--levels >= 0)
> +    {
> +      if (chdir ("..") != 0)
> +	{
> +	  printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n");
> +	  return;
> +	}
> +      if (remove (toolong_subdir) != 0)
> +	{
> +	  printf ("warning: could not remove subdirectory: %s: %m\n",
> +		  toolong_subdir);
> +	  return;
> +	}
> +    }
>  }

Throwing an warning should be fine in such cases.

>  
>  void
> @@ -123,6 +255,9 @@ support_delete_temp_files (void)
>  	 around, to prevent PID reuse.)  */
>        if (temp_name_list->owner == pid)
>  	{
> +	  if (temp_name_list->toolong)
> +	    remove_toolong_subdirs (temp_name_list->name);
> +
>  	  if (remove (temp_name_list->name) != 0)
>  	    printf ("warning: could not remove temporary file: %s: %m\n",
>  		    temp_name_list->name);
> @@ -147,3 +282,9 @@ support_print_temp_files (FILE *f)
>        fprintf (f, ")\n");
>      }
>  }
> +
> +void
> +support_set_test_dir (const char *path)
> +{
> +  test_dir = path;
> +}
> diff --git a/support/temp_file.h b/support/temp_file.h
> index 50a443abe4..de01fbbceb 100644
> --- a/support/temp_file.h
> +++ b/support/temp_file.h
> @@ -19,6 +19,8 @@
>  #ifndef SUPPORT_TEMP_FILE_H
>  #define SUPPORT_TEMP_FILE_H
>  
> +#include <limits.h>
> +#include <unistd.h>
>  #include <sys/cdefs.h>
>  
>  __BEGIN_DECLS
> @@ -44,6 +46,15 @@ int create_temp_file_in_dir (const char *base, const char *dir,
>     returns.  The caller should free this string.  */
>  char *support_create_temp_directory (const char *base);
>  
> +/* Create a temporary directory tree that is longer than PATH_MAX and schedule
> +   it for deletion.  BASENAME is used as a prefix for the unique directory
> +   name, which the function returns.  The caller should free this string.  */
> +char *support_create_and_chdir_toolong_temp_directory (const char *basename);
> +
> +/* Change into the innermost directory of the directory tree BASE, which was
> +   created using support_create_and_chdir_toolong_temp_directory.  */
> +void support_chdir_toolong_temp_directory (const char *base);
> +
>  __END_DECLS
>  
>  #endif /* SUPPORT_TEMP_FILE_H */