[PATCH] Access Control Lists for tmpfs

Add access control lists for tmpfs.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 97 insertions, 2 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index eda907c3a86a..b96de69f236b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -26,6 +26,8 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/fs.h>
+#include <linux/xattr.h>
+#include <linux/generic_acl.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/file.h>
@@ -177,6 +179,7 @@ static const struct address_space_operations shmem_aops;
 static struct file_operations shmem_file_operations;
 static struct inode_operations shmem_inode_operations;
 static struct inode_operations shmem_dir_inode_operations;
+static struct inode_operations shmem_special_inode_operations;
 static struct vm_operations_struct shmem_vm_ops;
 
 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
@@ -637,7 +640,7 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
         struct page *page = NULL;
         int error;
 
-        if (attr->ia_valid & ATTR_SIZE) {
+        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
                 if (attr->ia_size < inode->i_size) {
                         /*
                          * If truncating down to a partial page, then
@@ -670,6 +673,10 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
         error = inode_change_ok(inode, attr);
         if (!error)
                 error = inode_setattr(inode, attr);
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        if (!error && (attr->ia_valid & ATTR_MODE))
+                error = generic_acl_chmod(inode, &shmem_acl_ops);
+#endif
         if (page)
                 page_cache_release(page);
         return error;
@@ -1362,6 +1369,7 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
 
                 switch (mode & S_IFMT) {
                 default:
+                        inode->i_op = &shmem_special_inode_operations;
                         init_special_inode(inode, mode, dev);
                         break;
                 case S_IFREG:
@@ -1682,7 +1690,11 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
                                 iput(inode);
                                 return error;
                         }
-                        error = 0;
+                }
+                error = shmem_acl_init(inode, dir);
+                if (error) {
+                        iput(inode);
+                        return error;
                 }
                 if (dir->i_mode & S_ISGID) {
                         inode->i_gid = dir->i_gid;
@@ -1897,6 +1909,53 @@ static struct inode_operations shmem_symlink_inode_operations = {
         .put_link       = shmem_put_link,
 };
 
+#ifdef CONFIG_TMPFS_POSIX_ACL
+/**
+ * Superblocks without xattr inode operations will get security.* xattr
+ * support from the VFS "for free". As soon as we have any other xattrs
+ * like ACLs, we also need to implement the security.* handlers at
+ * filesystem level, though.
+ */
+
+static size_t shmem_xattr_security_list(struct inode *inode, char *list,
+                                        size_t list_len, const char *name,
+                                        size_t name_len)
+{
+        return security_inode_listsecurity(inode, list, list_len);
+}
+
+static int shmem_xattr_security_get(struct inode *inode, const char *name,
+                                    void *buffer, size_t size)
+{
+        if (strcmp(name, "") == 0)
+                return -EINVAL;
+        return security_inode_getsecurity(inode, name, buffer, size,
+                                          -EOPNOTSUPP);
+}
+
+static int shmem_xattr_security_set(struct inode *inode, const char *name,
+                                    const void *value, size_t size, int flags)
+{
+        if (strcmp(name, "") == 0)
+                return -EINVAL;
+        return security_inode_setsecurity(inode, name, value, size, flags);
+}
+
+struct xattr_handler shmem_xattr_security_handler = {
+        .prefix = XATTR_SECURITY_PREFIX,
+        .list   = shmem_xattr_security_list,
+        .get    = shmem_xattr_security_get,
+        .set    = shmem_xattr_security_set,
+};
+
+static struct xattr_handler *shmem_xattr_handlers[] = {
+        &shmem_xattr_acl_access_handler,
+        &shmem_xattr_acl_default_handler,
+        &shmem_xattr_security_handler,
+        NULL
+};
+#endif
+
 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
         int *policy, nodemask_t *policy_nodes)
@@ -2094,6 +2153,10 @@ static int shmem_fill_super(struct super_block *sb,
         sb->s_magic = TMPFS_MAGIC;
         sb->s_op = &shmem_ops;
         sb->s_time_gran = 1;
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        sb->s_xattr = shmem_xattr_handlers;
+        sb->s_flags |= MS_POSIXACL;
+#endif
 
         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
         if (!inode)
@@ -2130,6 +2193,7 @@ static void shmem_destroy_inode(struct inode *inode)
                 /* only struct inode is valid if it's an inline symlink */
                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
         }
+        shmem_acl_destroy_inode(inode);
         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
 }
 
@@ -2141,6 +2205,10 @@ static void init_once(void *foo, struct kmem_cache *cachep,
         if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
             SLAB_CTOR_CONSTRUCTOR) {
                 inode_init_once(&p->vfs_inode);
+#ifdef CONFIG_TMPFS_POSIX_ACL
+                p->i_acl = NULL;
+                p->i_default_acl = NULL;
+#endif
         }
 }
 
@@ -2184,6 +2252,14 @@ static struct inode_operations shmem_inode_operations = {
         .truncate       = shmem_truncate,
         .setattr        = shmem_notify_change,
         .truncate_range = shmem_truncate_range,
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
+
 };
 
 static struct inode_operations shmem_dir_inode_operations = {
@@ -2198,6 +2274,25 @@ static struct inode_operations shmem_dir_inode_operations = {
         .mknod          = shmem_mknod,
         .rename         = shmem_rename,
 #endif
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setattr        = shmem_notify_change,
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
+};
+
+static struct inode_operations shmem_special_inode_operations = {
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setattr        = shmem_notify_change,
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
 };
 
 static struct super_operations shmem_ops = {