linux-kernel - Re: [PATCH v6 09/40] xattr: handle idmapped mounts

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Date:   Wed, 03 Mar 2021 13:24:02 +0000
From:   David Howells <dhowells@...hat.com>
To:     Tycho Andersen <tycho@...ho.pizza>,
        Christian Brauner <christian.brauner@...ntu.com>
Cc:     dhowells@...hat.com, Tycho Andersen <tycho@...ho.ws>,
        James Morris <jmorris@...ei.org>,
        linux-fsdevel@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 09/40] xattr: handle idmapped mounts

Christian Brauner <christian.brauner@...ntu.com> wrote:

> diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
> index 72e42438f3d7..a591b5e09637 100644
> --- a/fs/cachefiles/xattr.c
> +++ b/fs/cachefiles/xattr.c
> @@ -39,8 +39,8 @@ int cachefiles_check_object_type(struct cachefiles_object *object)
>  	_enter("%p{%s}", object, type);
>  
>  	/* attempt to install a type label directly */
> -	ret = vfs_setxattr(dentry, cachefiles_xattr_cache, type, 2,
> -			   XATTR_CREATE);
> +	ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache, type,
> +			   2, XATTR_CREATE);

Actually, on further consideration, this might be the wrong thing to do in
cachefiles.  The creds are (or should be) overridden when accesses to the
underlying filesystem are being made.

I wonder if this should be using current_cred()->user_ns or
cache->cache_cred->user_ns instead.

David