[PATCH 3/4] io_uring/rw: use READ_ONCE with rw attributes

[Pavel Begunkov <asml.silence@xxxxxxxxx>]

In preparation to pre-mapped attributes read struct io_uring_attr_pi
with READ_ONCE and use an intermediate pointer.

Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
 io_uring/rw.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 75f70935ccf4..dc1acaf95db1 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -264,23 +264,29 @@ static inline void io_meta_restore(struct io_async_rw *io, struct kiocb *kiocb)
 static int io_prep_rw_pi(struct io_kiocb *req, struct io_rw *rw, int ddir,
 			 u64 attr_ptr, u64 attr_type_mask)
 {
-	struct io_uring_attr_pi pi_attr;
+	struct io_uring_attr_pi __pi_attr;
+	struct io_uring_attr_pi *pi_attr;
 	struct io_async_rw *io;
+	void __user *pi_addr;
+	size_t pi_len;
 	int ret;
 
-	if (copy_from_user(&pi_attr, u64_to_user_ptr(attr_ptr),
+	if (copy_from_user(&__pi_attr, u64_to_user_ptr(attr_ptr),
 	    sizeof(pi_attr)))
 		return -EFAULT;
+	pi_attr = &__pi_attr;
 
-	if (pi_attr.rsvd)
+	if (pi_attr->rsvd)
 		return -EINVAL;
 
 	io = req->async_data;
-	io->meta.flags = pi_attr.flags;
-	io->meta.app_tag = pi_attr.app_tag;
-	io->meta.seed = pi_attr.seed;
-	ret = import_ubuf(ddir, u64_to_user_ptr(pi_attr.addr),
-			  pi_attr.len, &io->meta.iter);
+	io->meta.flags = READ_ONCE(pi_attr->flags);
+	io->meta.app_tag = READ_ONCE(pi_attr->app_tag);
+	io->meta.seed = READ_ONCE(pi_attr->seed);
+
+	pi_addr = u64_to_user_ptr(READ_ONCE(pi_attr->addr));
+	pi_len = READ_ONCE(pi_attr->len);
+	ret = import_ubuf(ddir, pi_addr, pi_len, &io->meta.iter);
 	if (unlikely(ret < 0))
 		return ret;
 	req->flags |= REQ_F_HAS_METADATA;
-- 
2.47.1