Re: [PATCH 3/3] tools/nolibc: validate directory with O_DIRECTORY in opendir()

[David Laight]

On Mon, 31 Aug 2026 18:05:01 +0200
Thomas Weißschuh <linux@xxxxxxxxxxxxxx> wrote:

> fdopendir() requires a call to fstat() to determine if the opened file
> is a directory. Currently opendir() inherits this extra syscall.
> 
> Switch to O_DIRECTORY and remove the call to fdopendir() in opendir()
> to make the directory type check cheaper.

This should probably be the first patch.
With the changed fdopendir() it leaks an fd on error.
It also fixes the errno return.

David

> 
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> ---
>  tools/include/nolibc/dirent.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/include/nolibc/dirent.h b/tools/include/nolibc/dirent.h
> index 25fbff208998..2dbf4052b85a 100644
> --- a/tools/include/nolibc/dirent.h
> +++ b/tools/include/nolibc/dirent.h
> @@ -55,10 +55,11 @@ DIR *opendir(const char *name)
>  {
>  	int fd;
>  
> -	fd = open(name, O_RDONLY);
> +	fd = open(name, O_RDONLY | O_DIRECTORY);
>  	if (fd == -1)
>  		return NULL;
> -	return fdopendir(fd);
> +
> +	return (DIR *)(intptr_t)~fd;
>  }
>  
>  static __attribute__((unused))
>