linux-ext4 - Re: [PATCH v23 20/22] vfs: Add richacl permission checking

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Date:	Tue, 12 Jul 2016 08:13:54 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	Andreas Gruenbacher <agruenba@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Anna Schumaker <anna.schumaker@...app.com>,
	Dave Chinner <david@...morbit.com>, linux-ext4@...r.kernel.org,
	xfs@....sgi.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v23 20/22] vfs: Add richacl permission checking

On Thu, 2016-06-30 at 15:47 +0200, Andreas Gruenbacher wrote:
> Hook the richacl permission checking function into the vfs.
> 
> Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
> ---
>  fs/namei.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 52 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 7a822d0..48c9958 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -34,6 +34,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -256,7 +257,43 @@ void putname(struct filename *name)
>  		__putname(name);
>  }
>  
> -static int check_acl(struct inode *inode, int mask)
> +static int check_richacl(struct inode *inode, int mask)
> +{
> +#ifdef CONFIG_FS_RICHACL
> +	if (mask & MAY_NOT_BLOCK) {
> +		struct base_acl *base_acl;
> +
> +		base_acl = rcu_dereference(inode->i_acl);
> +		if (!base_acl)
> +			goto no_acl;
> +		/* no ->get_richacl() calls in RCU mode... */
> +		if (is_uncached_acl(base_acl))
> +			return -ECHILD;
> +		return richacl_permission(inode, richacl(base_acl),
> +					  mask & ~MAY_NOT_BLOCK);
> +	} else {
> +		struct richacl *acl;
> +
> +		acl = get_richacl(inode);
> +		if (IS_ERR(acl))
> +			return PTR_ERR(acl);
> +		if (acl) {
> +			int error = richacl_permission(inode, acl, mask);
> +			richacl_put(acl);
> +			return error;
> +		}
> +	}
> +no_acl:
> +#endif

nit: Can you move the above to a static inline or something that becomes a noop when the config var is turned off?

> +	if (mask & (MAY_DELETE_SELF | MAY_TAKE_OWNERSHIP |
> +		    MAY_CHMOD | MAY_SET_TIMES)) {
> +		/* File permission bits cannot grant this. */
> +		return -EACCES;
> +	}
> +	return -EAGAIN;
> +}
> +
> +static int check_posix_acl(struct inode *inode, int mask)
>  {
>  #ifdef CONFIG_FS_POSIX_ACL
>  	if (mask & MAY_NOT_BLOCK) {
> @@ -294,11 +331,24 @@ static int acl_permission_check(struct inode *inode, int mask)
>  {
>  	unsigned int mode = inode->i_mode;
>  
> +	/*
> +	 * With POSIX ACLs, the (mode & S_IRWXU) bits exactly match the owner
> +	 * permissions, and we can skip checking posix acls for the owner.
> +	 * With richacls, the owner may be granted fewer permissions than the
> +	 * mode bits seem to suggest (for example, append but not write), and
> +	 * we always need to check the richacl.
> +	 */
> +
> +	if (IS_RICHACL(inode)) {
> +		int error = check_richacl(inode, mask);
> +		if (error != -EAGAIN)
> +			return error;
> +	}
>  	if (likely(uid_eq(current_fsuid(), inode->i_uid)))
>  		mode >>= 6;
>  	else {
>  		if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
> -			int error = check_acl(inode, mask);
> +			int error = check_posix_acl(inode, mask);
>  			if (error != -EAGAIN)
>  				return error;
>  		}

Looks fine other than the nit above:

Reviewed-by: Jeff Layton <jlayton@...hat.com>
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