fs/9p: Add access = client option to opt in acl evaluation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

Documentation/filesystems/9p.txt

@@ -111,7 +111,7 @@ OPTIONS
   		This can be used to share devices/named pipes/sockets between
 		hosts.  This functionality will be expanded in later versions.
 
-  access	there are three access modes.
+  access	there are four access modes.
 			user  = if a user tries to access a file on v9fs
 			        filesystem for the first time, v9fs sends an
 			        attach command (Tattach) for that user.
@@ -120,6 +120,8 @@ OPTIONS
 				the files on the mounted filesystem
 			any   = v9fs does single attach and performs all
 				operations as one user
+			client = ACL based access check on the 9p client
+			         side for access validation
 
   cachetag	cache tag to use the specified persistent cache.
 		cache tags for existing cache sessions can be listed at

fs/9p/acl.c

@@ -22,6 +22,7 @@
 #include "xattr.h"
 #include "acl.h"
 #include "v9fs_vfs.h"
+#include "v9fs.h"
 
 static struct posix_acl *__v9fs_get_acl(struct p9_fid *fid, char *name)
 {
@@ -55,7 +56,14 @@ int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)
 {
 	int retval = 0;
 	struct posix_acl *pacl, *dacl;
+	struct v9fs_session_info *v9ses;
 
+	v9ses = v9fs_inode2v9ses(inode);
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) {
+		set_cached_acl(inode, ACL_TYPE_DEFAULT, NULL);
+		set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
+		return 0;
+	}
 	/* get the default/access acl values and cache them */
 	dacl = __v9fs_get_acl(fid, POSIX_ACL_XATTR_DEFAULT);
 	pacl = __v9fs_get_acl(fid, POSIX_ACL_XATTR_ACCESS);
@@ -85,7 +93,18 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
 
 int v9fs_check_acl(struct inode *inode, int mask)
 {
-	struct posix_acl *acl = v9fs_get_cached_acl(inode, ACL_TYPE_ACCESS);
+	struct posix_acl *acl;
+	struct v9fs_session_info *v9ses;
+
+	v9ses = v9fs_inode2v9ses(inode);
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) {
+		/*
+		 * On access = client mode get the acl
+		 * values from the server
+		 */
+		return 0;
+	}
+	acl = v9fs_get_cached_acl(inode, ACL_TYPE_ACCESS);
 
 	if (IS_ERR(acl))
 		return PTR_ERR(acl);
@@ -204,15 +223,41 @@ cleanup:
 
 }
 
+static int v9fs_remote_get_acl(struct dentry *dentry, const char *name,
+			       void *buffer, size_t size, int type)
+{
+	char *full_name;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		full_name =  POSIX_ACL_XATTR_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		full_name = POSIX_ACL_XATTR_DEFAULT;
+		break;
+	default:
+		BUG();
+	}
+	return v9fs_xattr_get(dentry, full_name, buffer, size);
+}
+
 static int v9fs_xattr_get_acl(struct dentry *dentry, const char *name,
 			      void *buffer, size_t size, int type)
 {
+	struct v9fs_session_info *v9ses;
 	struct posix_acl *acl;
 	int error;
 
 	if (strcmp(name, "") != 0)
 		return -EINVAL;
 
+	v9ses = v9fs_inode2v9ses(dentry->d_inode);
+	/*
+	 * We allow set/get/list of acl when access=client is not specified
+	 */
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
+		return v9fs_remote_get_acl(dentry, name, buffer, size, type);
+
 	acl = v9fs_get_cached_acl(dentry->d_inode, type);
 	if (IS_ERR(acl))
 		return PTR_ERR(acl);
@@ -224,16 +269,47 @@ static int v9fs_xattr_get_acl(struct dentry *dentry, const char *name,
 	return error;
 }
 
+static int v9fs_remote_set_acl(struct dentry *dentry, const char *name,
+			      const void *value, size_t size,
+			      int flags, int type)
+{
+	char *full_name;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		full_name =  POSIX_ACL_XATTR_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		full_name = POSIX_ACL_XATTR_DEFAULT;
+		break;
+	default:
+		BUG();
+	}
+	return v9fs_xattr_set(dentry, full_name, value, size, flags);
+}
+
+
 static int v9fs_xattr_set_acl(struct dentry *dentry, const char *name,
 			      const void *value, size_t size,
 			      int flags, int type)
 {
 	int retval;
 	struct posix_acl *acl;
+	struct v9fs_session_info *v9ses;
 	struct inode *inode = dentry->d_inode;
 
 	if (strcmp(name, "") != 0)
 		return -EINVAL;
+
+	v9ses = v9fs_inode2v9ses(dentry->d_inode);
+	/*
+	 * set the attribute on the remote. Without even looking at the
+	 * xattr value. We leave it to the server to validate
+	 */
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
+		return v9fs_remote_set_acl(dentry, name,
+					   value, size, flags, type);
+
 	if (S_ISLNK(inode->i_mode))
 		return -EOPNOTSUPP;
 	if (!is_owner_or_cap(inode))

fs/9p/fid.c

@@ -149,6 +149,7 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 	switch (access) {
 	case V9FS_ACCESS_SINGLE:
 	case V9FS_ACCESS_USER:
+	case V9FS_ACCESS_CLIENT:
 		uid = current_fsuid();
 		any = 0;
 		break;

fs/9p/v9fs.c

@@ -193,7 +193,17 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts)
 				v9ses->flags |= V9FS_ACCESS_USER;
 			else if (strcmp(s, "any") == 0)
 				v9ses->flags |= V9FS_ACCESS_ANY;
-			else {
+			else if (strcmp(s, "client") == 0) {
+#ifdef CONFIG_9P_FS_POSIX_ACL
+				v9ses->flags |= V9FS_ACCESS_CLIENT;
+#else
+				P9_DPRINTK(P9_DEBUG_ERROR,
+					"access=client option not supported\n");
+				kfree(s);
+				ret = -EINVAL;
+				goto free_and_return;
+#endif
+			} else {
 				v9ses->flags |= V9FS_ACCESS_SINGLE;
 				v9ses->uid = simple_strtoul(s, &e, 10);
 				if (*e != '\0')
@@ -278,6 +288,16 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
 
 	v9ses->maxdata = v9ses->clnt->msize - P9_IOHDRSZ;
 
+	if (!v9fs_proto_dotl(v9ses) &&
+	    ((v9ses->flags & V9FS_ACCESS_MASK) == V9FS_ACCESS_CLIENT)) {
+		/*
+		 * We support ACCESS_CLIENT only for dotl.
+		 * Fall back to ACCESS_USER
+		 */
+		v9ses->flags &= ~V9FS_ACCESS_MASK;
+		v9ses->flags |= V9FS_ACCESS_USER;
+	}
+	/*FIXME !! */
 	/* for legacy mode, fall back to V9FS_ACCESS_ANY */
 	if (!(v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) &&
 		((v9ses->flags&V9FS_ACCESS_MASK) == V9FS_ACCESS_USER)) {

fs/9p/v9fs.h

@@ -33,13 +33,17 @@
  *
  * Session flags reflect options selected by users at mount time
  */
+#define	V9FS_ACCESS_ANY (V9FS_ACCESS_SINGLE | \
+			 V9FS_ACCESS_USER |   \
+			 V9FS_ACCESS_CLIENT)
+#define V9FS_ACCESS_MASK V9FS_ACCESS_ANY
+
 enum p9_session_flags {
 	V9FS_PROTO_2000U	= 0x01,
 	V9FS_PROTO_2000L	= 0x02,
 	V9FS_ACCESS_SINGLE	= 0x04,
 	V9FS_ACCESS_USER	= 0x08,
-	V9FS_ACCESS_ANY		= 0x0C,
-	V9FS_ACCESS_MASK	= 0x0C,
+	V9FS_ACCESS_CLIENT	= 0x10
 };
 
 /* possible values of ->cache */

fs/9p/vfs_super.c

@@ -90,7 +90,8 @@ v9fs_fill_super(struct super_block *sb, struct v9fs_session_info *v9ses,
 	    MS_NOATIME;
 
 #ifdef CONFIG_9P_FS_POSIX_ACL
-	sb->s_flags |= MS_POSIXACL;
+	if ((v9ses->flags & V9FS_ACCESS_MASK) == V9FS_ACCESS_CLIENT)
+		sb->s_flags |= MS_POSIXACL;
 #endif
 
 	save_mount_options(sb, data);
@@ -181,7 +182,6 @@ static int v9fs_get_sb(struct file_system_type *fs_type, int flags,
 	retval = v9fs_get_acl(inode, fid);
 	if (retval)
 		goto release_sb;
-
 	v9fs_fid_add(root, fid);
 
 	P9_DPRINTK(P9_DEBUG_VFS, " simple set mount, return 0\n");