Re: [PATCH v6 1/4] openat2: new OPENAT2_REGULAR flag support

[Aleksa Sarai]

On 2026-03-28, Dorjoy Chowdhury <dorjoychy111@xxxxxxxxx> wrote:
> This flag indicates the path should be opened if it's a regular file.
> This is useful to write secure programs that want to avoid being
> tricked into opening device nodes with special semantics while thinking
> they operate on regular files. This is a requested feature from the
> uapi-group[1].
> 
> A corresponding error code EFTYPE has been introduced. For example, if
> openat2 is called on path /dev/null with OPENAT2_REGULAR in the flag
> param, it will return -EFTYPE. EFTYPE is already used in BSD systems
> like FreeBSD, macOS.
> 
> When used in combination with O_CREAT, either the regular file is
> created, or if the path already exists, it is opened if it's a regular
> file. Otherwise, -EFTYPE is returned.
> 
> When OPENAT2_REGULAR is combined with O_DIRECTORY, -EINVAL is returned
> as it doesn't make sense to open a path that is both a directory and a
> regular file.
> 
> [1]: https://uapi-group.org/kernel-features/#ability-to-only-open-regular-files
> 
> Signed-off-by: Dorjoy Chowdhury <dorjoychy111@xxxxxxxxx>
> ---

Aside from the nit below, feel free to take a

Reviewed-by: Aleksa Sarai <aleksa@xxxxxxxxxxxx>

> diff --git a/fs/open.c b/fs/open.c
> index 681d405bc61e..a6f445f72181 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -960,7 +960,7 @@ static int do_dentry_open(struct file *f,
>  	if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO)
>  		f->f_mode |= FMODE_CAN_ODIRECT;
>  
> -	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
> +	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | OPENAT2_REGULAR);

It's not clear to me why you dropped this, I didn't see a review
mentioning it either. (General note: Ideally the cover letter changelog
would mention who suggested a change in brackets after the changelog
line so it's easier to track where a change might've come from.)

I would personally keep it since O_DIRECTORY is not dropped (I do find
it interesting that O_EXCL is dropped too -- you could imagine a
userspace program wanting to know that the file was opened with O_EXCL,
though it provides you very little information).

-- 
Aleksa Sarai
https://www.cyphar.com/

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