io_uring/zcrx: fix area release on registration failure

On area registration failure there might be no ifq set and it's not safe
to access area->ifq in the release path without checking it first.

Cc: [email protected]
Fixes: f12ecf5 ("io_uring/zcrx: fix late dma unmap for a dead dev")
Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/bc02878678a5fec28bc77d33355cdba735418484.1748365640.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

io_uring/zcrx.c

@@ -366,7 +366,8 @@ static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
 
 static void io_zcrx_free_area(struct io_zcrx_area *area)
 {
-	io_zcrx_unmap_area(area->ifq, area);
+	if (area->ifq)
+		io_zcrx_unmap_area(area->ifq, area);
 	io_release_area_mem(&area->mem);
 
 	kvfree(area->freelist);