From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sat, 25 Jan 2020 19:34:01 +0000 (+0300)
Subject: io_uring: fix refcounting with batched allocations at OOM
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9466f43741bc08edd7b1bee642dd6f5561091634;p=linux.git

io_uring: fix refcounting with batched allocations at OOM

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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a700ee5fc89d6..1dd20305c6644 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4830,8 +4830,11 @@ 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)