On Wed, Apr 19, 2023 at 12:02 PM Sergey Bugaev <buga...@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.
