Add support to yaffs to set the security attribute of new inodes when
they are created.  This parallels similar support in other filesystems,
and is a requirement for e.g. SELinux and other MAC systems.

I'm not entirely sure about the error path in the unlikely case where
yaffs_init_security() returns an error; the intent is to unwind the file
creation in that situation as if it had never been created.  This error
case is however unlikely.  The file must have a security attribute
assigned before it becomes accessible to userspace.

I only updated yaffs_vfs_multi.c, but the same code should work for
yaffs_vfs_single.c, using whichever branch of the #if that corresponds
to your target upstream kernel version.

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>

---

 yaffs_vfs_multi.c |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 71 insertions(+), 2 deletions(-)

diff --git a/yaffs_vfs_multi.c b/yaffs_vfs_multi.c
index 7e28c40..5acd1de 100644
--- a/yaffs_vfs_multi.c
+++ b/yaffs_vfs_multi.c
@@ -78,6 +78,7 @@
 #include <linux/interrupt.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#include <linux/security.h>
 
 #if (YAFFS_NEW_FOLLOW_LINK == 1)
 #include <linux/namei.h>
@@ -1603,6 +1604,54 @@ out:
 	return ret_val;
 }
 
+#ifdef CONFIG_YAFFS_XATTR
+static int yaffs_init_security(struct inode *dir, struct dentry *dentry,
+			       struct inode *inode)
+{
+	int err;
+	size_t size;
+	void *value;
+	char *suffix;
+	char name[XATTR_NAME_MAX];
+	struct yaffs_dev *dev;
+	struct yaffs_obj *obj = yaffs_inode_to_obj(inode);
+	int result;
+
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 39))
+	err = security_inode_init_security(inode, dir, &dentry->d_name,
+					   &suffix, &value, &size);
+#else
+	err = security_inode_init_security(inode, dir, &suffix, &value, &size);
+#endif
+	if (err) {
+		if (err == -EOPNOTSUPP)
+			return 0;
+		return err;
+	}
+	snprintf(name, sizeof name, "%s%s", XATTR_SECURITY_PREFIX, suffix);
+
+	/* inlined yaffs_setxattr: no instantiated dentry yet */
+	dev = obj->my_dev;
+	yaffs_gross_lock(dev);
+	result = yaffs_set_xattrib(obj, name, value, size, 0);
+	if (result == YAFFS_OK)
+		err = 0;
+	else if (result < 0)
+		err = result;
+	yaffs_gross_unlock(dev);
+
+	kfree(value);
+	kfree(suffix);
+	return err;
+}
+#else
+static int yaffs_init_security(struct inode *dir, struct dentry *dentry,
+			       struct inode *inode)
+{
+	return 0;
+}
+#endif
+
 /*
  * File creation. Allocate an inode, and we're done..
  */
@@ -1689,6 +1738,15 @@ static int yaffs_mknod(struct inode *dir, struct dentry *dentry, int mode,
 
 	if (obj) {
 		inode = yaffs_get_inode(dir->i_sb, mode, rdev, obj);
+		error = yaffs_init_security(dir, dentry, inode);
+		if (error) {
+			/* undo! */
+			iput(inode);
+			yaffs_gross_lock(dev);
+			yaffs_unlinker(parent, dentry->d_name.name);
+			yaffs_gross_unlock(dev);
+			return error;
+		}
 		d_instantiate(dentry, inode);
 		update_dir_time(dir);
 		yaffs_trace(YAFFS_TRACE_OS,
@@ -1802,12 +1860,14 @@ static int yaffs_symlink(struct inode *dir, struct dentry *dentry,
 	uid_t uid = YCRED(current)->fsuid;
 	gid_t gid =
 	    (dir->i_mode & S_ISGID) ? dir->i_gid : YCRED(current)->fsgid;
+	struct yaffs_obj *parent = yaffs_inode_to_obj(dir);
+	int error;
 
 	yaffs_trace(YAFFS_TRACE_OS, "yaffs_symlink");
 
-	dev = yaffs_inode_to_obj(dir)->my_dev;
+	dev = parent->my_dev;
 	yaffs_gross_lock(dev);
-	obj = yaffs_create_symlink(yaffs_inode_to_obj(dir), dentry->d_name.name,
+	obj = yaffs_create_symlink(parent, dentry->d_name.name,
 				   S_IFLNK | S_IRWXUGO, uid, gid, symname);
 	yaffs_gross_unlock(dev);
 
@@ -1815,6 +1875,15 @@ static int yaffs_symlink(struct inode *dir, struct dentry *dentry,
 		struct inode *inode;
 
 		inode = yaffs_get_inode(dir->i_sb, obj->yst_mode, 0, obj);
+		error = yaffs_init_security(dir, dentry, inode);
+		if (error) {
+			/* undo! */
+			iput(inode);
+			yaffs_gross_lock(dev);
+			yaffs_unlinker(parent, dentry->d_name.name);
+			yaffs_gross_unlock(dev);
+			return error;
+		}
 		d_instantiate(dentry, inode);
 		update_dir_time(dir);
 		yaffs_trace(YAFFS_TRACE_OS, "symlink created OK");


-- 
Stephen Smalley
National Security Agency