[PATCH] Generic VFS fallback for security xattrs

This patch modifies the VFS setxattr, getxattr, and listxattr code to fall
back to the security module for security xattrs if the filesystem does not
support xattrs natively.  This allows security modules to export the incore
inode security label information to userspace even if the filesystem does
not provide xattr storage, and eliminates the need to individually patch
various pseudo filesystem types to provide such access.  The patch removes
the existing xattr code from devpts and tmpfs as it is then no longer
needed.

The patch restructures the code flow slightly to reduce duplication between
the normal path and the fallback path, but this should only have one
user-visible side effect - a program may get -EACCES rather than
-EOPNOTSUPP if policy denied access but the filesystem didn't support the
operation anyway.  Note that the post_setxattr hook call is not needed in
the fallback case, as the inode_setsecurity hook call handles the incore
inode security state update directly.  In contrast, we do call fsnotify in
both cases.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 0 insertions, 69 deletions

diff --git a/fs/devpts/Makefile b/fs/devpts/Makefile
index 5800df2e50c8..236696efcbac 100644
--- a/fs/devpts/Makefile
+++ b/fs/devpts/Makefile
@@ -5,4 +5,3 @@
 obj-$(CONFIG_UNIX98_PTYS)               += devpts.o
 
 devpts-$(CONFIG_UNIX98_PTYS)            := inode.o
-devpts-$(CONFIG_DEVPTS_FS_SECURITY)     += xattr_security.o
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 1571c8d6c232..f2be44d4491f 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -18,28 +18,9 @@
 #include <linux/mount.h>
 #include <linux/tty.h>
 #include <linux/devpts_fs.h>
-#include <linux/xattr.h>
 
 #define DEVPTS_SUPER_MAGIC 0x1cd1
 
-extern struct xattr_handler devpts_xattr_security_handler;
-
-static struct xattr_handler *devpts_xattr_handlers[] = {
-#ifdef CONFIG_DEVPTS_FS_SECURITY
-        &devpts_xattr_security_handler,
-#endif
-        NULL
-};
-
-static struct inode_operations devpts_file_inode_operations = {
-#ifdef CONFIG_DEVPTS_FS_XATTR
-        .setxattr       = generic_setxattr,
-        .getxattr       = generic_getxattr,
-        .listxattr      = generic_listxattr,
-        .removexattr    = generic_removexattr,
-#endif
-};
-
 static struct vfsmount *devpts_mnt;
 static struct dentry *devpts_root;
 
@@ -102,7 +83,6 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
         s->s_blocksize_bits = 10;
         s->s_magic = DEVPTS_SUPER_MAGIC;
         s->s_op = &devpts_sops;
-        s->s_xattr = devpts_xattr_handlers;
         s->s_time_gran = 1;
 
         inode = new_inode(s);
@@ -175,7 +155,6 @@ int devpts_pty_new(struct tty_struct *tty)
         inode->i_gid = config.setgid ? config.gid : current->fsgid;
         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
         init_special_inode(inode, S_IFCHR|config.mode, device);
-        inode->i_op = &devpts_file_inode_operations;
         inode->u.generic_ip = tty;
 
         dentry = get_node(number);
diff --git a/fs/devpts/xattr_security.c b/fs/devpts/xattr_security.c
deleted file mode 100644
index 864cb5c79baa..000000000000
--- a/fs/devpts/xattr_security.c
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * Security xattr support for devpts.
- *
- * Author: Stephen Smalley <sds@epoch.ncsc.mil>
- * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the Free
- * Software Foundation; either version 2 of the License, or (at your option)
- * any later version.
- */
-#include <linux/string.h>
-#include <linux/fs.h>
-#include <linux/security.h>
-#include <linux/xattr.h>
-
-static size_t
-devpts_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
-devpts_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);
-}
-
-static int
-devpts_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 devpts_xattr_security_handler = {
-        .prefix = XATTR_SECURITY_PREFIX,
-        .list   = devpts_xattr_security_list,
-        .get    = devpts_xattr_security_get,
-        .set    = devpts_xattr_security_set,
-};