io_uring: fix sq array offset calculation

rings_size() sets sq_offset to the total size of the rings (the returned
value which is used for memory allocation). This is wrong: sq array should
be located within the rings, not after them. Set sq_offset to where it
should be.

Fixes: 75b28aff ("io_uring: allocate the two rings together")
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Hristo Venev <hristo@venev.name>
Cc: io-uring@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -7416,6 +7416,9 @@ static unsigned long rings_size(unsigned sq_entries, unsigned cq_entries,
 		return SIZE_MAX;
 #endif
 
+	if (sq_offset)
+		*sq_offset = off;
+
 	sq_array_size = array_size(sizeof(u32), sq_entries);
 	if (sq_array_size == SIZE_MAX)
 		return SIZE_MAX;
@@ -7423,9 +7426,6 @@ static unsigned long rings_size(unsigned sq_entries, unsigned cq_entries,
 	if (check_add_overflow(off, sq_array_size, &off))
 		return SIZE_MAX;
 
-	if (sq_offset)
-		*sq_offset = off;
-
 	return off;
 }