linux-kernel - Re: [PATCH] vfs: reorder checks in may_create_in

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Date: Thu, 20 Jun 2024 14:46:33 +0200
From: Jan Kara <jack@...e.cz>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] vfs: reorder checks in may_create_in_sticky

On Thu 20-06-24 14:03:59, Mateusz Guzik wrote:
> The routine is called for all directories on file creation and weirdly
> postpones the check if the dir is sticky to begin with. Instead it first
> checks fifos and regular files (in that order), while avoidably pulling
> globals.
> 
> No functional changes.
> 
> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>

Yeah, putting the sticky bit check first makes sense also logically. Feel
free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/namei.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 63d1fb06da6b..b1600060ecfb 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1246,9 +1246,9 @@ static int may_create_in_sticky(struct mnt_idmap *idmap,
>  	umode_t dir_mode = nd->dir_mode;
>  	vfsuid_t dir_vfsuid = nd->dir_vfsuid;
>  
> -	if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
> -	    (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
> -	    likely(!(dir_mode & S_ISVTX)) ||
> +	if (likely(!(dir_mode & S_ISVTX)) ||
> +	    (S_ISREG(inode->i_mode) && !sysctl_protected_regular) ||
> +	    (S_ISFIFO(inode->i_mode) && !sysctl_protected_fifos) ||
>  	    vfsuid_eq(i_uid_into_vfsuid(idmap, inode), dir_vfsuid) ||
>  	    vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
>  		return 0;
> -- 
> 2.43.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR