[RFC 3/7] io_uring: fail loop_rw_iter with pure bvec bufs

[Pavel Begunkov <asml.silence@gmail.com>]

There will be registered buffers that have never had a userspace mapping
and to use them the file have to work with iterators. Fail
loop_rw_iter() if it meets such a buffer.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/rw.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 6c7d2654770e..b2ad99e0e304 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -428,11 +428,18 @@ static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
  */
 static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
 {
+	struct io_kiocb *req = cmd_to_io_kiocb(rw);
 	struct kiocb *kiocb = &rw->kiocb;
 	struct file *file = kiocb->ki_filp;
 	ssize_t ret = 0;
 	loff_t *ppos;
 
+	if (req->opcode == IORING_OP_READ_FIXED ||
+	    req->opcode == IORING_OP_WRITE_FIXED) {
+		if (!req->imu->ubuf)
+			return -EFAULT;
+	}
+
 	/*
 	 * Don't support polled IO through this interface, and we can't
 	 * support non-blocking either. For the latter, this just causes
-- 
2.40.0