linux-kernel - Re: [PATCH] fs/mnt_idmapping.c: Return -EINVAL when no map is written

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Date: Tue, 6 Feb 2024 17:06:12 +0100
From: Christian Brauner <brauner@...nel.org>
To: taylor.a.jackson@...com
Cc: Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	Seth Forshee <sforshee@...nel.org>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/mnt_idmapping.c: Return -EINVAL when no map is written

On Tue, Feb 06, 2024 at 03:17:52PM +0000, Taylor Jackson via B4 Relay wrote:
> From: Taylor Jackson <taylor.a.jackson@...com>
> 
> This change will return an "invalid argument" error code when a map is
> not provided when attempting to remap files using the id mapped mount
> command, rather than returning nothing.

That should probably explain that before this change it was possible to
create an idmapped mount such that none of the inode's {g,u}id were
mapped and that now this is no longer possible.

> 
> Signed-off-by: Taylor Jackson <taylor.a.jackson@...com>
> ---

Yup, that looks good to me. It seems unlikely that someone wants none of
the files in that mount to map to anything,

Reviewed-by: Christian Brauner <brauner@...nel.org>

>  fs/mnt_idmapping.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/mnt_idmapping.c b/fs/mnt_idmapping.c
> index 64c5205e2b5e..3c60f1eaca61 100644
> --- a/fs/mnt_idmapping.c
> +++ b/fs/mnt_idmapping.c
> @@ -214,7 +214,7 @@ static int copy_mnt_idmap(struct uid_gid_map *map_from,
>  	 * anything at all.
>  	 */
>  	if (nr_extents == 0)
> -		return 0;
> +		return -EINVAL;
>  
>  	/*
>  	 * Here we know that nr_extents is greater than zero which means
> 
> ---
> base-commit: 54be6c6c5ae8e0d93a6c4641cb7528eb0b6ba478
> change-id: 20240206-mnt-idmap-inval-18d3a35f83fd
> 
> Best regards,
> -- 
> Taylor Jackson <taylor.a.jackson@...com>
>