1 files changed, 51 insertions, 34 deletions

diff --git a/fs/xattr.c b/fs/xattr.c
index 61107b6bbed2..df3af9fa8c77 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -80,6 +80,31 @@ xattr_resolve_name(struct inode *inode, const char **name)
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+/**
+ * may_write_xattr - check whether inode allows writing xattr
+ * @mnt_userns:	User namespace of the mount the inode was found from
+ * @inode: the inode on which to set an xattr
+ *
+ * Check whether the inode allows writing xattrs. Specifically, we can never
+ * set or remove an extended attribute on a read-only filesystem  or on an
+ * immutable / append-only inode.
+ *
+ * We also need to ensure that the inode has a mapping in the mount to
+ * not risk writing back invalid i_{g,u}id values.
+ *
+ * Return: On success zero is returned. On error a negative errno is returned.
+ */
+int may_write_xattr(struct user_namespace *mnt_userns, struct inode *inode)
+{
+	if (IS_IMMUTABLE(inode))
+		return -EPERM;
+	if (IS_APPEND(inode))
+		return -EPERM;
+	if (HAS_UNMAPPED_ID(mnt_userns, inode))
+		return -EPERM;
+	return 0;
+}
+
 /*
  * Check permissions for extended attribute access.  This is a bit complicated
  * because different namespaces have very different rules.
@@ -88,20 +113,12 @@ static int
 xattr_permission(struct user_namespace *mnt_userns, 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_IMMUTABLE(inode) || IS_APPEND(inode))
-			return -EPERM;
-		/*
-		 * Updating an xattr will likely cause i_uid and i_gid
-		 * to be writen back improperly if their true value is
-		 * unknown to the vfs.
-		 */
-		if (HAS_UNMAPPED_ID(mnt_userns, inode))
-			return -EPERM;
+		int ret;
+
+		ret = may_write_xattr(mnt_userns, inode);
+		if (ret)
+			return ret;
 	}
 
 	/*
@@ -172,6 +189,9 @@ __vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 {
 	const struct xattr_handler *handler;
 
+	if (is_posix_acl_xattr(name))
+		return -EOPNOTSUPP;
+
 	handler = xattr_resolve_name(inode, &name);
 	if (IS_ERR(handler))
 		return PTR_ERR(handler);
@@ -282,12 +302,6 @@ out:
 }
 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 
-static inline bool is_posix_acl_xattr(const char *name)
-{
-	return (strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
-	       (strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT) == 0);
-}
-
 int
 vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 	     const char *name, const void *value, size_t size, int flags)
@@ -399,6 +413,9 @@ __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 {
 	const struct xattr_handler *handler;
 
+	if (is_posix_acl_xattr(name))
+		return -EOPNOTSUPP;
+
 	handler = xattr_resolve_name(inode, &name);
 	if (IS_ERR(handler))
 		return PTR_ERR(handler);
@@ -437,10 +454,7 @@ vfs_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		return ret;
 	}
 nolsm:
-	error = __vfs_getxattr(dentry, inode, name, value, size);
-	if (error > 0 && is_posix_acl_xattr(name))
-		posix_acl_getxattr_idmapped_mnt(mnt_userns, inode, value, size);
-	return error;
+	return __vfs_getxattr(dentry, inode, name, value, size);
 }
 EXPORT_SYMBOL_GPL(vfs_getxattr);
 
@@ -471,6 +485,9 @@ __vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 	struct inode *inode = d_inode(dentry);
 	const struct xattr_handler *handler;
 
+	if (is_posix_acl_xattr(name))
+		return -EOPNOTSUPP;
+
 	handler = xattr_resolve_name(inode, &name);
 	if (IS_ERR(handler))
 		return PTR_ERR(handler);
@@ -580,17 +597,13 @@ int setxattr_copy(const char __user *name, struct xattr_ctx *ctx)
 	return error;
 }
 
-static void setxattr_convert(struct user_namespace *mnt_userns,
-			     struct dentry *d, struct xattr_ctx *ctx)
-{
-	if (ctx->size && is_posix_acl_xattr(ctx->kname->name))
-		posix_acl_fix_xattr_from_user(ctx->kvalue, ctx->size);
-}
-
 int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		struct xattr_ctx *ctx)
 {
-	setxattr_convert(mnt_userns, dentry, ctx);
+	if (is_posix_acl_xattr(ctx->kname->name))
+		return do_set_acl(mnt_userns, dentry, ctx->kname->name,
+				  ctx->kvalue, ctx->size);
+
 	return vfs_setxattr(mnt_userns, dentry, ctx->kname->name,
 			ctx->kvalue, ctx->size, ctx->flags);
 }
@@ -697,10 +710,11 @@ do_getxattr(struct user_namespace *mnt_userns, struct dentry *d,
 			return -ENOMEM;
 	}
 
-	error = vfs_getxattr(mnt_userns, d, kname, ctx->kvalue, ctx->size);
+	if (is_posix_acl_xattr(ctx->kname->name))
+		error = do_get_acl(mnt_userns, d, kname, ctx->kvalue, ctx->size);
+	else
+		error = vfs_getxattr(mnt_userns, d, kname, ctx->kvalue, ctx->size);
 	if (error > 0) {
-		if (is_posix_acl_xattr(kname))
-			posix_acl_fix_xattr_to_user(ctx->kvalue, error);
 		if (ctx->size && copy_to_user(ctx->value, ctx->kvalue, error))
 			error = -EFAULT;
 	} else if (error == -ERANGE && ctx->size >= XATTR_SIZE_MAX) {
@@ -875,6 +889,9 @@ removexattr(struct user_namespace *mnt_userns, struct dentry *d,
 	if (error < 0)
 		return error;
 
+	if (is_posix_acl_xattr(kname))
+		return vfs_remove_acl(mnt_userns, d, kname);
+
 	return vfs_removexattr(mnt_userns, d, kname);
 }