[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>

1 files changed, 0 insertions, 85 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 08a3bc2..bdc4bbb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -45,7 +45,6 @@
 #include <linux/swapops.h>
 #include <linux/mempolicy.h>
 #include <linux/namei.h>
-#include <linux/xattr.h>
 #include <asm/uaccess.h>
 #include <asm/div64.h>
 #include <asm/pgtable.h>
@@ -179,7 +178,6 @@ static 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 = {
@@ -1300,7 +1298,6 @@ 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:
@@ -1804,12 +1801,6 @@ static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *co
 static struct inode_operations shmem_symlink_inline_operations = {
 	.readlink	= generic_readlink,
 	.follow_link	= shmem_follow_link_inline,
-#ifdef CONFIG_TMPFS_XATTR
-	.setxattr       = generic_setxattr,
-	.getxattr       = generic_getxattr,
-	.listxattr      = generic_listxattr,
-	.removexattr    = generic_removexattr,
-#endif
 };
 
 static struct inode_operations shmem_symlink_inode_operations = {
@@ -1817,12 +1808,6 @@ static struct inode_operations shmem_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.follow_link	= shmem_follow_link,
 	.put_link	= shmem_put_link,
-#ifdef CONFIG_TMPFS_XATTR
-	.setxattr       = generic_setxattr,
-	.getxattr       = generic_getxattr,
-	.listxattr      = generic_listxattr,
-	.removexattr    = generic_removexattr,
-#endif
 };
 
 static int shmem_parse_options(char *options, int *mode, uid_t *uid, gid_t *gid, unsigned long *blocks, unsigned long *inodes)
@@ -1942,12 +1927,6 @@ static void shmem_put_super(struct super_block *sb)
 	sb->s_fs_info = NULL;
 }
 
-#ifdef CONFIG_TMPFS_XATTR
-static struct xattr_handler *shmem_xattr_handlers[];
-#else
-#define shmem_xattr_handlers NULL
-#endif
-
 static int shmem_fill_super(struct super_block *sb,
 			    void *data, int silent)
 {
@@ -1998,7 +1977,6 @@ static int shmem_fill_super(struct super_block *sb,
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = TMPFS_MAGIC;
 	sb->s_op = &shmem_ops;
-	sb->s_xattr = shmem_xattr_handlers;
 
 	inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
 	if (!inode)
@@ -2087,12 +2065,6 @@ static struct file_operations shmem_file_operations = {
 static struct inode_operations shmem_inode_operations = {
 	.truncate	= shmem_truncate,
 	.setattr	= shmem_notify_change,
-#ifdef CONFIG_TMPFS_XATTR
-	.setxattr       = generic_setxattr,
-	.getxattr       = generic_getxattr,
-	.listxattr      = generic_listxattr,
-	.removexattr    = generic_removexattr,
-#endif
 };
 
 static struct inode_operations shmem_dir_inode_operations = {
@@ -2106,21 +2078,6 @@ static struct inode_operations shmem_dir_inode_operations = {
 	.rmdir		= shmem_rmdir,
 	.mknod		= shmem_mknod,
 	.rename		= shmem_rename,
-#ifdef CONFIG_TMPFS_XATTR
-	.setxattr       = generic_setxattr,
-	.getxattr       = generic_getxattr,
-	.listxattr      = generic_listxattr,
-	.removexattr    = generic_removexattr,
-#endif
-#endif
-};
-
-static struct inode_operations shmem_special_inode_operations = {
-#ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
-	.listxattr	= generic_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 };
 
@@ -2146,48 +2103,6 @@ static struct vm_operations_struct shmem_vm_ops = {
 };
 
 
-#ifdef CONFIG_TMPFS_SECURITY
-
-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);
-}
-
-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);
-}
-
-static 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,
-};
-
-#endif	/* CONFIG_TMPFS_SECURITY */
-
-#ifdef CONFIG_TMPFS_XATTR
-
-static struct xattr_handler *shmem_xattr_handlers[] = {
-#ifdef CONFIG_TMPFS_SECURITY
-	&shmem_xattr_security_handler,
-#endif
-	NULL
-};
-
-#endif	/* CONFIG_TMPFS_XATTR */
-
 static struct super_block *shmem_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data)
 {