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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, Pavel Begunkov <asml.silence@gmail.com>,
        Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 02/16] io_uring: fix linked deferred ->files cancellation
Date:   Fri, 11 Sep 2020 14:47:19 +0200
Message-Id: <20200911122459.714236078@linuxfoundation.org>
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From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit c127a2a1b7baa5eb40a7e2de4b7f0c51ccbbb2ef ]

While looking for ->files in ->defer_list, consider that requests there
may actually be links.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/io_uring.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5f627194d0920..d05023ca74bdc 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7601,6 +7601,28 @@ static bool io_match_link(struct io_kiocb *preq, struct io_kiocb *req)
 	return false;
 }
 
+static inline bool io_match_files(struct io_kiocb *req,
+				       struct files_struct *files)
+{
+	return (req->flags & REQ_F_WORK_INITIALIZED) && req->work.files == files;
+}
+
+static bool io_match_link_files(struct io_kiocb *req,
+				struct files_struct *files)
+{
+	struct io_kiocb *link;
+
+	if (io_match_files(req, files))
+		return true;
+	if (req->flags & REQ_F_LINK_HEAD) {
+		list_for_each_entry(link, &req->link_list, link_list) {
+			if (io_match_files(link, files))
+				return true;
+		}
+	}
+	return false;
+}
+
 /*
  * We're looking to cancel 'req' because it's holding on to our files, but
  * 'req' could be a link to another request. See if it is, and cancel that
@@ -7683,8 +7705,7 @@ static void io_cancel_defer_files(struct io_ring_ctx *ctx,
 
 	spin_lock_irq(&ctx->completion_lock);
 	list_for_each_entry_reverse(req, &ctx->defer_list, list) {
-		if ((req->flags & REQ_F_WORK_INITIALIZED)
-			&& req->work.files == files) {
+		if (io_match_link_files(req, files)) {
 			list_cut_position(&list, &ctx->defer_list, &req->list);
 			break;
 		}
-- 
2.25.1