io_uring/rsrc: check for nonconsecutive pages

commit 776617d upstream.

Pages that are from the same folio do not necessarily need to be
consecutive. In that case, we cannot consolidate them into a single bvec
entry. Before applying the huge page optimization from commit 57bebf8
("io_uring/rsrc: optimise registered huge pages"), check that the memory
is actually consecutive.

Cc: stable@vger.kernel.org
Fixes: 57bebf8 ("io_uring/rsrc: optimise registered huge pages")
Signed-off-by: Tobias Holl <tobias@tholl.xyz>
[axboe: formatting]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

io_uring/rsrc.c

@@ -1230,7 +1230,12 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
 	if (nr_pages > 1) {
 		folio = page_folio(pages[0]);
 		for (i = 1; i < nr_pages; i++) {
-			if (page_folio(pages[i]) != folio) {
+			/*
+			 * Pages must be consecutive and on the same folio for
+			 * this to work
+			 */
+			if (page_folio(pages[i]) != folio ||
+			    pages[i] != pages[i - 1] + 1) {
 				folio = NULL;
 				break;
 			}