1 files changed, 147 insertions, 54 deletions

diff --git a/fs/xattr.c b/fs/xattr.c
index a9db225..80eca7d 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -19,6 +19,149 @@
 #include <linux/fsnotify.h>
 #include <asm/uaccess.h>
 
+
+/*
+ * Check permissions for extended attribute access.  This is a bit complicated
+ * because different namespaces have very different rules.
+ */
+static int
+xattr_permission(struct inode *inode, const char *name, int mask)
+{
+	/*
+	 * We can never set or remove an extended attribute on a read-only
+	 * filesystem  or on an immutable / append-only inode.
+	 */
+	if (mask & MAY_WRITE) {
+		if (IS_RDONLY(inode))
+			return -EROFS;
+		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+			return -EPERM;
+	}
+
+	/*
+	 * No restriction for security.* and system.* from the VFS.  Decision
+	 * on these is left to the underlying filesystem / security module.
+	 */
+	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
+	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+		return 0;
+
+	/*
+	 * The trusted.* namespace can only accessed by a privilegued user.
+	 */
+	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+		return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
+
+	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
+		if (!S_ISREG(inode->i_mode) &&
+		    (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX))
+			return -EPERM;
+	}
+
+	return permission(inode, mask, NULL);
+}
+
+int
+vfs_setxattr(struct dentry *dentry, char *name, void *value,
+		size_t size, int flags)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	error = xattr_permission(inode, name, MAY_WRITE);
+	if (error)
+		return error;
+
+	mutex_lock(&inode->i_mutex);
+	error = security_inode_setxattr(dentry, name, value, size, flags);
+	if (error)
+		goto out;
+	error = -EOPNOTSUPP;
+	if (inode->i_op->setxattr) {
+		error = inode->i_op->setxattr(dentry, name, value, size, flags);
+		if (!error) {
+			fsnotify_xattr(dentry);
+			security_inode_post_setxattr(dentry, name, value,
+						     size, flags);
+		}
+	} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
+				XATTR_SECURITY_PREFIX_LEN)) {
+		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+		error = security_inode_setsecurity(inode, suffix, value,
+						   size, flags);
+		if (!error)
+			fsnotify_xattr(dentry);
+	}
+out:
+	mutex_unlock(&inode->i_mutex);
+	return error;
+}
+EXPORT_SYMBOL_GPL(vfs_setxattr);
+
+ssize_t
+vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	error = xattr_permission(inode, name, MAY_READ);
+	if (error)
+		return error;
+
+	error = security_inode_getxattr(dentry, name);
+	if (error)
+		return error;
+
+	if (inode->i_op->getxattr)
+		error = inode->i_op->getxattr(dentry, name, value, size);
+	else
+		error = -EOPNOTSUPP;
+
+	if (!strncmp(name, XATTR_SECURITY_PREFIX,
+				XATTR_SECURITY_PREFIX_LEN)) {
+		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+		int ret = security_inode_getsecurity(inode, suffix, value,
+						     size, error);
+		/*
+		 * Only overwrite the return value if a security module
+		 * is actually active.
+		 */
+		if (ret != -EOPNOTSUPP)
+			error = ret;
+	}
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(vfs_getxattr);
+
+int
+vfs_removexattr(struct dentry *dentry, char *name)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	if (!inode->i_op->removexattr)
+		return -EOPNOTSUPP;
+
+	error = xattr_permission(inode, name, MAY_WRITE);
+	if (error)
+		return error;
+
+	error = security_inode_removexattr(dentry, name);
+	if (error)
+		return error;
+
+	mutex_lock(&inode->i_mutex);
+	error = inode->i_op->removexattr(dentry, name);
+	mutex_unlock(&inode->i_mutex);
+
+	if (!error)
+		fsnotify_xattr(dentry);
+	return error;
+}
+EXPORT_SYMBOL_GPL(vfs_removexattr);
+
+
 /*
  * Extended attribute SET operations
  */
@@ -51,29 +194,7 @@ setxattr(struct dentry *d, char __user *name, void __user *value,
 		}
 	}
 
-	down(&d->d_inode->i_sem);
-	error = security_inode_setxattr(d, kname, kvalue, size, flags);
-	if (error)
-		goto out;
-	error = -EOPNOTSUPP;
-	if (d->d_inode->i_op && d->d_inode->i_op->setxattr) {
-		error = d->d_inode->i_op->setxattr(d, kname, kvalue,
-						   size, flags);
-		if (!error) {
-			fsnotify_xattr(d);
-			security_inode_post_setxattr(d, kname, kvalue,
-						     size, flags);
-		}
-	} else if (!strncmp(kname, XATTR_SECURITY_PREFIX,
-			    sizeof XATTR_SECURITY_PREFIX - 1)) {
-		const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
-		error = security_inode_setsecurity(d->d_inode, suffix, kvalue,
-						   size, flags);
-		if (!error)
-			fsnotify_xattr(d);
-	}
-out:
-	up(&d->d_inode->i_sem);
+	error = vfs_setxattr(d, kname, kvalue, size, flags);
 	kfree(kvalue);
 	return error;
 }
@@ -147,22 +268,7 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
 			return -ENOMEM;
 	}
 
-	error = security_inode_getxattr(d, kname);
-	if (error)
-		goto out;
-	error = -EOPNOTSUPP;
-	if (d->d_inode->i_op && d->d_inode->i_op->getxattr)
-		error = d->d_inode->i_op->getxattr(d, kname, kvalue, size);
-
-	if (!strncmp(kname, XATTR_SECURITY_PREFIX,
-		     sizeof XATTR_SECURITY_PREFIX - 1)) {
-		const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
-		int rv = security_inode_getsecurity(d->d_inode, suffix, kvalue,
-						    size, error);
-		/* Security module active: overwrite error value */
-		if (rv != -EOPNOTSUPP)
-			error = rv;
-	}
+	error = vfs_getxattr(d, kname, kvalue, size);
 	if (error > 0) {
 		if (size && copy_to_user(value, kvalue, error))
 			error = -EFAULT;
@@ -171,7 +277,6 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
 		   than XATTR_SIZE_MAX bytes. Not possible. */
 		error = -E2BIG;
 	}
-out:
 	kfree(kvalue);
 	return error;
 }
@@ -245,7 +350,7 @@ listxattr(struct dentry *d, char __user *list, size_t size)
 		error = d->d_inode->i_op->listxattr(d, klist, size);
 	} else {
 		error = security_inode_listsecurity(d->d_inode, klist, size);
-		if (size && error >= size)
+		if (size && error > size)
 			error = -ERANGE;
 	}
 	if (error > 0) {
@@ -318,19 +423,7 @@ removexattr(struct dentry *d, char __user *name)
 	if (error < 0)
 		return error;
 
-	error = -EOPNOTSUPP;
-	if (d->d_inode->i_op && d->d_inode->i_op->removexattr) {
-		error = security_inode_removexattr(d, kname);
-		if (error)
-			goto out;
-		down(&d->d_inode->i_sem);
-		error = d->d_inode->i_op->removexattr(d, kname);
-		up(&d->d_inode->i_sem);
-		if (!error)
-			fsnotify_xattr(d);
-	}
-out:
-	return error;
+	return vfs_removexattr(d, kname);
 }
 
 asmlinkage long