[RFC PATCH 1/4] security: modify security_inode_init_security to return an array of xattrs

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

Option 1:

In preparation for supporting the initialization of multiple LSM xattrs
and the EVM xattr, this patch defines an xattr structure and changes the
security_inode_init_security() API to return an array of xattrs.

Until multiple LSM support is upstreamed, to avoid allocating/freeing the
xattr array, define the xattr array in the security_inode_init_security()
caller, not security_inode_init_security.

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
---
 fs/ext3/xattr_security.c |   33 ++++++++++++++++++++-------------
 fs/ext4/xattr_security.c |   33 ++++++++++++++++++++-------------
 include/linux/security.h |   10 +++++-----
 include/linux/xattr.h    |    6 ++++++
 mm/shmem.c               |    7 +++----
 security/security.c      |   17 +++++++++++++----
 6 files changed, 67 insertions(+), 39 deletions(-)

diff --git a/fs/ext3/xattr_security.c b/fs/ext3/xattr_security.c
index b8d9f83..cb26a02 100644
--- a/fs/ext3/xattr_security.c
+++ b/fs/ext3/xattr_security.c
@@ -52,22 +52,29 @@ int
 ext3_init_security(handle_t *handle, struct inode *inode, struct inode *dir,
 		   const struct qstr *qstr)
 {
+	struct xattr new_xattrs[MAX_LSM_XATTR + 1];
+	struct xattr *xattr_array = &new_xattrs[0], *xattr;
 	int err;
-	size_t len;
-	void *value;
-	char *name;
 
-	err = security_inode_init_security(inode, dir, qstr, &name, &value, &len);
-	if (err) {
-		if (err == -EOPNOTSUPP)
-			return 0;
-		return err;
+	memset(new_xattrs, 0, sizeof new_xattrs);
+	err = security_inode_init_security(inode, dir, qstr, &xattr_array);
+	if (err)
+		goto out;
+
+	for (xattr = new_xattrs; xattr->name != NULL; xattr++) {
+		err = ext3_xattr_set_handle(handle, inode,
+					    EXT3_XATTR_INDEX_SECURITY,
+					    xattr->name, xattr->value,
+					    xattr->value_len, 0);
+		if (err < 0)
+			break;
+	}
+out:
+	for (xattr = new_xattrs; xattr->name != NULL; xattr++) {
+		kfree(xattr->value);
+		kfree(xattr->name);
 	}
-	err = ext3_xattr_set_handle(handle, inode, EXT3_XATTR_INDEX_SECURITY,
-				    name, value, len, 0);
-	kfree(name);
-	kfree(value);
-	return err;
+	return (err == -EOPNOTSUPP) ? 0 : err;
 }
 
 const struct xattr_handler ext3_xattr_security_handler = {
diff --git a/fs/ext4/xattr_security.c b/fs/ext4/xattr_security.c
index 007c3bf..ccf3347 100644
--- a/fs/ext4/xattr_security.c
+++ b/fs/ext4/xattr_security.c
@@ -52,22 +52,29 @@ int
 ext4_init_security(handle_t *handle, struct inode *inode, struct inode *dir,
 		   const struct qstr *qstr)
 {
+	struct xattr new_xattrs[MAX_LSM_XATTR + 1];
+	struct xattr *xattr_array = &new_xattrs[0], *xattr;
 	int err;
-	size_t len;
-	void *value;
-	char *name;
 
-	err = security_inode_init_security(inode, dir, qstr, &name, &value, &len);
-	if (err) {
-		if (err == -EOPNOTSUPP)
-			return 0;
-		return err;
+	memset(new_xattrs, 0, sizeof new_xattrs);
+	err = security_inode_init_security(inode, dir, qstr, &xattr_array);
+	if (err)
+		goto out;
+
+	for (xattr = new_xattrs; xattr->name != NULL; xattr++) {
+		err = ext4_xattr_set_handle(handle, inode,
+					    EXT4_XATTR_INDEX_SECURITY,
+					    xattr->name, xattr->value,
+					    xattr->value_len, 0);
+		if (err < 0)
+			break;
+	}
+out:
+	for (xattr = new_xattrs; xattr->name != NULL; xattr++) {
+		kfree(xattr->name);
+		kfree(xattr->value);
 	}
-	err = ext4_xattr_set_handle(handle, inode, EXT4_XATTR_INDEX_SECURITY,
-				    name, value, len, 0);
-	kfree(name);
-	kfree(value);
-	return err;
+	return (err == -EOPNOTSUPP) ? 0 : err;
 }
 
 const struct xattr_handler ext4_xattr_security_handler = {
diff --git a/include/linux/security.h b/include/linux/security.h
index 8ce59ef..bf593c1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -36,10 +36,12 @@
 #include <linux/key.h>
 #include <linux/xfrm.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
 #include <net/flow.h>
 
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
+#define MAX_LSM_XATTR	1
 
 /* If capable should audit the security request */
 #define SECURITY_CAP_NOAUDIT 0
@@ -1704,8 +1706,8 @@ int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
 int security_inode_alloc(struct inode *inode);
 void security_inode_free(struct inode *inode);
 int security_inode_init_security(struct inode *inode, struct inode *dir,
-				 const struct qstr *qstr, char **name,
-				 void **value, size_t *len);
+				 const struct qstr *qstr,
+				 struct xattr **xattr_array);
 int security_inode_create(struct inode *dir, struct dentry *dentry, int mode);
 int security_inode_link(struct dentry *old_dentry, struct inode *dir,
 			 struct dentry *new_dentry);
@@ -2035,9 +2037,7 @@ static inline void security_inode_free(struct inode *inode)
 static inline int security_inode_init_security(struct inode *inode,
 						struct inode *dir,
 						const struct qstr *qstr,
-						char **name,
-						void **value,
-						size_t *len)
+						struct xattr **xattr_array)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index aed54c5..7a37866 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -67,6 +67,12 @@ struct xattr_handler {
 		   size_t size, int flags, int handler_flags);
 };
 
+struct xattr {
+	char *name;
+	void *value;
+	size_t value_len;
+};
+
 ssize_t xattr_getsecurity(struct inode *, const char *, void *, size_t);
 ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
 ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
diff --git a/mm/shmem.c b/mm/shmem.c
index d221a1c..1d585b3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1877,8 +1877,7 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
 	if (inode) {
 		error = security_inode_init_security(inode, dir,
-						     &dentry->d_name, NULL,
-						     NULL, NULL);
+						     &dentry->d_name, NULL);
 		if (error) {
 			if (error != -EOPNOTSUPP) {
 				iput(inode);
@@ -2017,8 +2016,8 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
 	if (!inode)
 		return -ENOSPC;
 
-	error = security_inode_init_security(inode, dir, &dentry->d_name, NULL,
-					     NULL, NULL);
+	error = security_inode_init_security(inode, dir, &dentry->d_name,
+					     NULL);
 	if (error) {
 		if (error != -EOPNOTSUPP) {
 			iput(inode);
diff --git a/security/security.c b/security/security.c
index 4ba6d4c..28842f2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -339,13 +339,22 @@ void security_inode_free(struct inode *inode)
 }
 
 int security_inode_init_security(struct inode *inode, struct inode *dir,
-				 const struct qstr *qstr, char **name,
-				 void **value, size_t *len)
+				 const struct qstr *qstr,
+				 struct xattr **xattr_array)
 {
+	struct xattr *lsm_xattr;
+
 	if (unlikely(IS_PRIVATE(inode)))
 		return -EOPNOTSUPP;
-	return security_ops->inode_init_security(inode, dir, qstr, name, value,
-						 len);
+
+	if (!xattr_array)
+		return security_ops->inode_init_security(inode, dir, qstr,
+							 NULL, NULL, NULL);
+	lsm_xattr = *xattr_array;
+	return security_ops->inode_init_security(inode, dir, qstr,
+						 &lsm_xattr->name,
+						 &lsm_xattr->value,
+						 &lsm_xattr->value_len);
 }
 EXPORT_SYMBOL(security_inode_init_security);
 
-- 
1.7.3.4