Re: [RFC PATCH v2 4/7] csu: Fix standard fds' mode

["Cristian Rodríguez" <crrodriguez@opensuse.org>]

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On Wed, Apr 19, 2023 at 12:02 PM Sergey Bugaev <bugaevc@gmail.com> wrote:

> stdin is supposed to be readable, stdout and stderr writable. Otherwise,
> we get this:
>
> index de6dd716..ca4812cd 100644
> --- a/csu/check_fds.c
> +++ b/csu/check_fds.c
> @@ -90,7 +90,7 @@ __libc_check_standard_fds (void)
>       is really paranoid but some people actually are.  If /dev/null
>       should happen to be a symlink to somewhere else and not the
>       device commonly known as "/dev/null" we bail out.  */
> -  check_one_fd (STDIN_FILENO, O_WRONLY | O_NOFOLLOW);
> -  check_one_fd (STDOUT_FILENO, O_RDONLY | O_NOFOLLOW);
> -  check_one_fd (STDERR_FILENO, O_RDONLY | O_NOFOLLOW);
> +  check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
> +  check_one_fd (STDOUT_FILENO, O_WRONLY | O_NOFOLLOW);
> +  check_one_fd (STDERR_FILENO, O_WRONLY | O_NOFOLLOW);
>  }
> --
> 2.40.0
>

Im a little bit lost on what it was supposed to do in this old form..  as
the open flags are all wrong..

Changelog says:

 (__libc_check_standard_fds): Reverse modes so that common operations on
        the descriptors fail.

So this was intended at some point in the past decades to make it fail..  I
see it is used only for SUID statically linked binaries. is this really
needed now? playing silly games with this fds will always result in silly
prices.