io_uring: fix refcounting with batched allocations at OOM

to #26323588

commit 9466f43741bc08edd7b1bee642dd6f5561091634 upstream.

In case of out of memory the second argument of percpu_ref_put_many() in
io_submit_sqes() may evaluate into "nr - (-EAGAIN)", that is clearly
wrong.

Fixes: 2b85edfc0c90 ("io_uring: batch getting pcpu references")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>

fs/io_uring.c

@@ -4827,8 +4827,11 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 			break;
 	}
 
-	if (submitted != nr)
-		percpu_ref_put_many(&ctx->refs, nr - submitted);
+	if (unlikely(submitted != nr)) {
+		int ref_used = (submitted == -EAGAIN) ? 0 : submitted;
+
+		percpu_ref_put_many(&ctx->refs, nr - ref_used);
+	}
 	if (link)
 		io_queue_link_head(link);
 	if (statep)