linux-kernel - [PATCH v27 18/21] vfs: Add richacl permission checking

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Message-Id: <1476190256-1677-19-git-send-email-agruenba@redhat.com>
Date:   Tue, 11 Oct 2016 14:50:53 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>
Cc:     Andreas Gruenbacher <agruenba@...hat.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        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: [PATCH v27 18/21] vfs: Add richacl permission checking

Hook the richacl permission checking function into the vfs.

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...hat.com>
---
 fs/namei.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 7b8e00d7..9808154c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -34,6 +34,7 @@
 #include <linux/device_cgroup.h>
 #include <linux/fs_struct.h>
 #include <linux/posix_acl.h>
+#include <linux/richacl.h>
 #include <linux/hash.h>
 #include <linux/bitops.h>
 #include <linux/init_task.h>
@@ -257,7 +258,43 @@ 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
+	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) {
@@ -295,11 +332,24 @@ 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;
 		}
-- 
2.7.4