Re: [PATCH v10 4/5] io_uring: add fsetxattr and setxattr support

On Thu, Dec 30, 2021 at 02:17:23AM +0000, Al Viro wrote:

quoted

+static int io_setxattr_prep(struct io_kiocb *req,
+			const struct io_uring_sqe *sqe)
+{
+	struct io_xattr *ix = &req->xattr;
+	const char __user *path;
+	int ret;
+
+	ret = __io_setxattr_prep(req, sqe);
+	if (ret)
+		return ret;
+
+	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
+
+	ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
+	if (IS_ERR(ix->filename)) {
+		ret = PTR_ERR(ix->filename);
+		ix->filename = NULL;
+	}
+
+	return ret;
+}

... and here you use it and bring the pathname in.  Should the latter
step fail, you restore ->filename to NULL and return an error.

Could you explain what kind of magic could allow the caller to tell
whether ix->ctx.kname needs to be freed on error?  I don't see any way
that could possibly work...

getxattr side has the same problem, AFAICS...