fs/9p: Implement POSIX ACL permission checking function

The ACL value is fetched as a part of inode initialization
from the server and the permission checking function use the
cached value of the ACL

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>

8 files changed, 186 insertions, 22 deletions

diff --git a/fs/9p/Kconfig b/fs/9p/Kconfig
index 795233702a4e..7e0511476797 100644
--- a/fs/9p/Kconfig
+++ b/fs/9p/Kconfig
@@ -17,3 +17,16 @@ config 9P_FSCACHE
           Choose Y here to enable persistent, read-only local
           caching support for 9p clients using FS-Cache
 
+
+config 9P_FS_POSIX_ACL
+        bool "9P POSIX Access Control Lists"
+        depends on 9P_FS
+        select FS_POSIX_ACL
+        help
+          POSIX Access Control Lists (ACLs) support permissions for users and
+          groups beyond the owner/group/world scheme.
+
+          To learn more about Access Control Lists, visit the POSIX ACLs for
+          Linux website <http://acl.bestbits.at/>.
+
+          If you don't know what Access Control Lists are, say N
diff --git a/fs/9p/Makefile b/fs/9p/Makefile
index 91fba025fcbe..f8ba37effd1b 100644
--- a/fs/9p/Makefile
+++ b/fs/9p/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_9P_FS) := 9p.o
         xattr_user.o
 
 9p-$(CONFIG_9P_FSCACHE) += cache.o
+9p-$(CONFIG_9P_FS_POSIX_ACL) += acl.o
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
new file mode 100644
index 000000000000..a8c013615a22
--- /dev/null
+++ b/fs/9p/acl.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include <linux/slab.h>
+#include <linux/posix_acl_xattr.h>
+#include "xattr.h"
+#include "acl.h"
+
+static struct posix_acl *__v9fs_get_acl(struct p9_fid *fid, char *name)
+{
+        ssize_t size;
+        void *value = NULL;
+        struct posix_acl *acl = NULL;;
+
+        size = v9fs_fid_xattr_get(fid, name, NULL, 0);
+        if (size > 0) {
+                value = kzalloc(size, GFP_NOFS);
+                if (!value)
+                        return ERR_PTR(-ENOMEM);
+                size = v9fs_fid_xattr_get(fid, name, value, size);
+                if (size > 0) {
+                        acl = posix_acl_from_xattr(value, size);
+                        if (IS_ERR(acl))
+                                goto err_out;
+                }
+        } else if (size == -ENODATA || size == 0 ||
+                   size == -ENOSYS || size == -EOPNOTSUPP) {
+                acl = NULL;
+        } else
+                acl = ERR_PTR(-EIO);
+
+err_out:
+        kfree(value);
+        return acl;
+}
+
+int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)
+{
+        int retval = 0;
+        struct posix_acl *pacl, *dacl;
+
+        /* 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);
+
+        if (!IS_ERR(dacl) && !IS_ERR(pacl)) {
+                set_cached_acl(inode, ACL_TYPE_DEFAULT, dacl);
+                set_cached_acl(inode, ACL_TYPE_ACCESS, pacl);
+                posix_acl_release(dacl);
+                posix_acl_release(pacl);
+        } else
+                retval = -EIO;
+
+        return retval;
+}
+
+static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
+{
+        struct posix_acl *acl;
+        /*
+         * 9p Always cache the acl value when
+         * instantiating the inode (v9fs_inode_from_fid)
+         */
+        acl = get_cached_acl(inode, type);
+        BUG_ON(acl == ACL_NOT_CACHED);
+        return acl;
+}
+
+int v9fs_check_acl(struct inode *inode, int mask)
+{
+        struct posix_acl *acl = v9fs_get_cached_acl(inode, ACL_TYPE_ACCESS);
+
+        if (IS_ERR(acl))
+                return PTR_ERR(acl);
+        if (acl) {
+                int error = posix_acl_permission(inode, acl, mask);
+                posix_acl_release(acl);
+                return error;
+        }
+        return -EAGAIN;
+}
diff --git a/fs/9p/acl.h b/fs/9p/acl.h
new file mode 100644
index 000000000000..b1414f7c82e0
--- /dev/null
+++ b/fs/9p/acl.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+#ifndef FS_9P_ACL_H
+#define FS_9P_ACL_H
+
+#ifdef CONFIG_9P_FS_POSIX_ACL
+extern int v9fs_get_acl(struct inode *, struct p9_fid *);
+extern int v9fs_check_acl(struct inode *inode, int mask);
+#else
+#define v9fs_check_acl NULL
+static inline int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)
+{
+        return 0;
+}
+#endif
+#endif /* FS_9P_XATTR_H */
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index c3d200d41dca..1249b8323961 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -36,6 +36,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/xattr.h>
+#include <linux/posix_acl.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
 
@@ -44,6 +45,7 @@
 #include "fid.h"
 #include "cache.h"
 #include "xattr.h"
+#include "acl.h"
 
 static const struct inode_operations v9fs_dir_inode_operations;
 static const struct inode_operations v9fs_dir_inode_operations_dotu;
@@ -500,6 +502,11 @@ v9fs_inode_dotl(struct v9fs_session_info *v9ses, struct p9_fid *fid,
         v9fs_vcookie_set_qid(ret, &st->qid);
         v9fs_cache_inode_get_cookie(ret);
 #endif
+        err = v9fs_get_acl(ret, fid);
+        if (err) {
+                iput(ret);
+                goto error;
+        }
         kfree(st);
         return ret;
 error:
@@ -1959,7 +1966,7 @@ static const struct inode_operations v9fs_dir_inode_operations_dotl = {
         .getxattr = generic_getxattr,
         .removexattr = generic_removexattr,
         .listxattr = v9fs_listxattr,
-
+        .check_acl = v9fs_check_acl,
 };
 
 static const struct inode_operations v9fs_dir_inode_operations = {
@@ -1986,6 +1993,7 @@ static const struct inode_operations v9fs_file_inode_operations_dotl = {
         .getxattr = generic_getxattr,
         .removexattr = generic_removexattr,
         .listxattr = v9fs_listxattr,
+        .check_acl = v9fs_check_acl,
 };
 
 static const struct inode_operations v9fs_symlink_inode_operations = {
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 1d12ba0ed3db..14da5778d44e 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -46,6 +46,7 @@
 #include "v9fs_vfs.h"
 #include "fid.h"
 #include "xattr.h"
+#include "acl.h"
 
 static const struct super_operations v9fs_super_ops, v9fs_super_ops_dotl;
 
@@ -88,6 +89,10 @@ v9fs_fill_super(struct super_block *sb, struct v9fs_session_info *v9ses,
         sb->s_flags = flags | MS_ACTIVE | MS_SYNCHRONOUS | MS_DIRSYNC |
             MS_NOATIME;
 
+#ifdef CONFIG_9P_FS_POSIX_ACL
+        sb->s_flags |= MS_POSIXACL;
+#endif
+
         save_mount_options(sb, data);
 }
 
@@ -149,7 +154,6 @@ static int v9fs_get_sb(struct file_system_type *fs_type, int flags,
                 goto release_sb;
         }
         sb->s_root = root;
-
         if (v9fs_proto_dotl(v9ses)) {
                 struct p9_stat_dotl *st = NULL;
                 st = p9_client_getattr_dotl(fid, P9_STATS_BASIC);
@@ -174,6 +178,9 @@ static int v9fs_get_sb(struct file_system_type *fs_type, int flags,
                 p9stat_free(st);
                 kfree(st);
         }
+        retval = v9fs_get_acl(inode, fid);
+        if (retval)
+                goto release_sb;
 
         v9fs_fid_add(root, fid);
 
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index f88e5c2dc873..67ac6cfc1a07 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -21,30 +21,13 @@
 #include "fid.h"
 #include "xattr.h"
 
-/*
- * v9fs_xattr_get()
- *
- * Copy an extended attribute into the buffer
- * provided, or compute the buffer size required.
- * Buffer is NULL to compute the size of the buffer required.
- *
- * Returns a negative error number on failure, or the number of bytes
- * used / required on success.
- */
-ssize_t v9fs_xattr_get(struct dentry *dentry, const char *name,
-                       void *buffer, size_t buffer_size)
+ssize_t v9fs_fid_xattr_get(struct p9_fid *fid, const char *name,
+                           void *buffer, size_t buffer_size)
 {
         ssize_t retval;
         int msize, read_count;
         u64 offset = 0, attr_size;
-        struct p9_fid *fid, *attr_fid;
-
-        P9_DPRINTK(P9_DEBUG_VFS, "%s: name = %s value_len = %zu\n",
-                __func__, name, buffer_size);
-
-        fid = v9fs_fid_lookup(dentry);
-        if (IS_ERR(fid))
-                return PTR_ERR(fid);
+        struct p9_fid *attr_fid;
 
         attr_fid = p9_client_xattrwalk(fid, name, &attr_size);
         if (IS_ERR(attr_fid)) {
@@ -88,6 +71,31 @@ error:
 
 }
 
+
+/*
+ * v9fs_xattr_get()
+ *
+ * Copy an extended attribute into the buffer
+ * provided, or compute the buffer size required.
+ * Buffer is NULL to compute the size of the buffer required.
+ *
+ * Returns a negative error number on failure, or the number of bytes
+ * used / required on success.
+ */
+ssize_t v9fs_xattr_get(struct dentry *dentry, const char *name,
+                       void *buffer, size_t buffer_size)
+{
+        struct p9_fid *fid;
+
+        P9_DPRINTK(P9_DEBUG_VFS, "%s: name = %s value_len = %zu\n",
+                __func__, name, buffer_size);
+        fid = v9fs_fid_lookup(dentry);
+        if (IS_ERR(fid))
+                return PTR_ERR(fid);
+
+        return v9fs_fid_xattr_get(fid, name, buffer, buffer_size);
+}
+
 /*
  * v9fs_xattr_set()
  *
diff --git a/fs/9p/xattr.h b/fs/9p/xattr.h
index 9ddf672ae5c4..ec908c693342 100644
--- a/fs/9p/xattr.h
+++ b/fs/9p/xattr.h
@@ -15,10 +15,14 @@
 #define FS_9P_XATTR_H
 
 #include <linux/xattr.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
 
 extern const struct xattr_handler *v9fs_xattr_handlers[];
 extern struct xattr_handler v9fs_xattr_user_handler;
 
+extern ssize_t v9fs_fid_xattr_get(struct p9_fid *, const char *,
+                                  void *, size_t);
 extern ssize_t v9fs_xattr_get(struct dentry *, const char *,
                               void *, size_t);
 extern int v9fs_xattr_set(struct dentry *, const char *,