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

[Jeff Layton]

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@xxxxxxxxxx>
> ---
> Âfs/namei.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
> Â1 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 @@
> Â#include 
> Â#include 
> Â#include 
> +#include 
> Â#include 
> Â#include 
> Â#include 
> @@ -256,7 +257,43 @@ void putname(struct filename *name)
> Â		__putname(name);
> Â}
> Â
> -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),
> +					ÂÂmask & ~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 |
> +		ÂÂÂÂMAY_CHMOD | MAY_SET_TIMES)) {
> +		/* File permission bits cannot grant this. */
> +		return -EACCES;
> +	}
> +	return -EAGAIN;
> +}
> +
> +static int check_posix_acl(struct inode *inode, int mask)
> Â{
> Â#ifdef CONFIG_FS_POSIX_ACL
> Â	if (mask & MAY_NOT_BLOCK) {
> @@ -294,11 +331,24 @@ static int acl_permission_check(struct inode *inode, int mask)
> Â{
> Â	unsigned int mode = inode->i_mode;
> Â
> +	/*
> +	Â* With POSIX ACLs, the (mode & S_IRWXU) bits exactly match the owner
> +	Â* permissions, and we can skip checking posix acls for the owner.
> +	Â* With richacls, the owner may be granted fewer permissions than the
> +	Â* mode bits seem to suggest (for example, append but not write), and
> +	Â* we always need to check the richacl.
> +	Â*/
> +
> +	if (IS_RICHACL(inode)) {
> +		int error = check_richacl(inode, mask);
> +		if (error != -EAGAIN)
> +			return error;
> +	}
> Â	if (likely(uid_eq(current_fsuid(), inode->i_uid)))
> Â		mode >>= 6;
> Â	else {
> Â		if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
> -			int error = check_acl(inode, mask);
> +			int error = check_posix_acl(inode, mask);
> Â			if (error != -EAGAIN)
> Â				return error;
> Â		}

Looks fine other than the nit above:

Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>