io_uring/region: fix error codes after failed vmap

io_create_region() jumps after a vmap failure without setting the return
code, it could be 0 or just uninitialised.

Fixes: dfbbfbf ("io_uring: introduce concept of memory regions")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/0abac19dbf81c061cffaa9534a2471ed5460ad3e.1731803848.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/memmap.c

@@ -247,8 +247,10 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
 	}
 
 	vptr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
-	if (!vptr)
+	if (!vptr) {
+		ret = -ENOMEM;
 		goto out_free;
+	}
 
 	mr->pages = pages;
 	mr->vmap_ptr = vptr;