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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hao Xu <haoxu@linux.alibaba.com>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 5.16 0071/1039] io_uring: fix no lock protection for ctx->cq_extra
Date:   Mon, 24 Jan 2022 19:31:00 +0100
Message-Id: <20220124184127.559922995@linuxfoundation.org>
In-Reply-To: <20220124184125.121143506@linuxfoundation.org>
References: <20220124184125.121143506@linuxfoundation.org>
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From: Hao Xu <haoxu@linux.alibaba.com>

commit e302f1046f4c209291b07ff7bc4d15ca26891f16 upstream.

ctx->cq_extra should be protected by completion lock so that the
req_need_defer() does the right check.

Cc: stable@vger.kernel.org
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20211125092103.224502-2-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/io_uring.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6544,12 +6544,15 @@ static __cold void io_drain_req(struct i
 	u32 seq = io_get_sequence(req);
 
 	/* Still need defer if there is pending req in defer list. */
+	spin_lock(&ctx->completion_lock);
 	if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list)) {
+		spin_unlock(&ctx->completion_lock);
 queue:
 		ctx->drain_active = false;
 		io_req_task_queue(req);
 		return;
 	}
+	spin_unlock(&ctx->completion_lock);
 
 	ret = io_req_prep_async(req);
 	if (ret) {