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>, stable@kernel.org
Subject: [PATCH 5.15 038/179] io_uring: correct link-list traversal locking
Date:   Mon, 29 Nov 2021 19:17:12 +0100
Message-Id: <20211129181720.215225353@linuxfoundation.org>
In-Reply-To: <20211129181718.913038547@linuxfoundation.org>
References: <20211129181718.913038547@linuxfoundation.org>
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From: Pavel Begunkov <asml.silence@gmail.com>

commit 674ee8e1b4a41d2fdffc885c55350c3fbb38c22a upstream.

As io_remove_next_linked() is now under ->timeout_lock (see
io_link_timeout_fn), we should update locking around io_for_each_link()
and io_match_task() to use the new lock.

Cc: stable@kernel.org # 5.15+
Fixes: 89850fce16a1a ("io_uring: run timeouts from task_work")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b54541cedf7de59cb5ae36109e58529ca16e66aa.1637631883.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/io_uring.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1430,10 +1430,10 @@ static void io_prep_async_link(struct io
 	if (req->flags & REQ_F_LINK_TIMEOUT) {
 		struct io_ring_ctx *ctx = req->ctx;
 
-		spin_lock(&ctx->completion_lock);
+		spin_lock_irq(&ctx->timeout_lock);
 		io_for_each_link(cur, req)
 			io_prep_async_work(cur);
-		spin_unlock(&ctx->completion_lock);
+		spin_unlock_irq(&ctx->timeout_lock);
 	} else {
 		io_for_each_link(cur, req)
 			io_prep_async_work(cur);
@@ -5697,6 +5697,7 @@ static bool io_poll_remove_all(struct io
 	int posted = 0, i;
 
 	spin_lock(&ctx->completion_lock);
+	spin_lock_irq(&ctx->timeout_lock);
 	for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
 		struct hlist_head *list;
 
@@ -5706,6 +5707,7 @@ static bool io_poll_remove_all(struct io
 				posted += io_poll_remove_one(req);
 		}
 	}
+	spin_unlock_irq(&ctx->timeout_lock);
 	spin_unlock(&ctx->completion_lock);
 
 	if (posted)
@@ -9523,9 +9525,9 @@ static bool io_cancel_task_cb(struct io_
 		struct io_ring_ctx *ctx = req->ctx;
 
 		/* protect against races with linked timeouts */
-		spin_lock(&ctx->completion_lock);
+		spin_lock_irq(&ctx->timeout_lock);
 		ret = io_match_task(req, cancel->task, cancel->all);
-		spin_unlock(&ctx->completion_lock);
+		spin_unlock_irq(&ctx->timeout_lock);
 	} else {
 		ret = io_match_task(req, cancel->task, cancel->all);
 	}
@@ -9539,12 +9541,14 @@ static bool io_cancel_defer_files(struct
 	LIST_HEAD(list);
 
 	spin_lock(&ctx->completion_lock);
+	spin_lock_irq(&ctx->timeout_lock);
 	list_for_each_entry_reverse(de, &ctx->defer_list, list) {
 		if (io_match_task(de->req, task, cancel_all)) {
 			list_cut_position(&list, &ctx->defer_list, &de->list);
 			break;
 		}
 	}
+	spin_unlock_irq(&ctx->timeout_lock);
 	spin_unlock(&ctx->completion_lock);
 	if (list_empty(&list))
 		return false;