linux-kernel - Re: [PATCH v2 10/13] ceph: allow idmapped setattr inode op

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Date:   Fri, 2 Jun 2023 09:30:37 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Cc:     brauner@...nel.org, stgraber@...ntu.com,
        linux-fsdevel@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/13] ceph: allow idmapped setattr inode op


On 5/24/23 23:33, Alexander Mikhalitsyn wrote:
> From: Christian Brauner <christian.brauner@...ntu.com>
>
> Enable __ceph_setattr() to handle idmapped mounts. This is just a matter
> of passing down the mount's idmapping.
>
> Cc: Jeff Layton <jlayton@...nel.org>
> Cc: Ilya Dryomov <idryomov@...il.com>
> Cc: ceph-devel@...r.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
>   fs/ceph/inode.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 37e1cbfc7c89..f1f934439be0 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -2050,6 +2050,13 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
>   
>   	dout("setattr %p issued %s\n", inode, ceph_cap_string(issued));
>   
> +	/*
> +	 * The attr->ia_{g,u}id members contain the target {g,u}id we're
> +	 * sending over the wire. The mount idmapping only matters when we
> +	 * create new filesystem objects based on the caller's mapped
> +	 * fs{g,u}id.
> +	 */
> +	req->r_mnt_idmap = &nop_mnt_idmap;

For example with an idmapping 1000:0 and in the /mnt/idmapped_ceph/.

This means the "__ceph_setattr()" will always use UID 0 to set the 
caller_uid, right ? If it is then the client auth checking for the 
setattr requests in cephfs MDS will succeed, since the UID 0 is root. 
But if you use a different idmapping, such as 1000:2000, it will fail.

So here IMO we should set it to 'idmap' too ?

Thanks

- Xiubo

>   	if (ia_valid & ATTR_UID) {
>   		dout("setattr %p uid %d -> %d\n", inode,
>   		     from_kuid(&init_user_ns, inode->i_uid),
> @@ -2240,7 +2247,7 @@ int ceph_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>   	if (ceph_inode_is_shutdown(inode))
>   		return -ESTALE;
>   
> -	err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
> +	err = setattr_prepare(idmap, dentry, attr);
>   	if (err != 0)
>   		return err;
>   
> @@ -2255,7 +2262,7 @@ int ceph_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>   	err = __ceph_setattr(inode, attr);
>   
>   	if (err >= 0 && (attr->ia_valid & ATTR_MODE))
> -		err = posix_acl_chmod(&nop_mnt_idmap, dentry, attr->ia_mode);
> +		err = posix_acl_chmod(idmap, dentry, attr->ia_mode);
>   
>   	return err;
>   }