[PATCH 1/1] io_uring: correct link-list traversal locking

[PATCH 1/1] io_uring: correct link-list traversal locking

[Pavel Begunkov]

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>
---
 fs/io_uring.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e98e7ce3dc39..a4c508a1e0cf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1502,10 +1502,10 @@ static void io_prep_async_link(struct io_kiocb *req)
 	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);
@@ -5699,6 +5699,7 @@ static __cold bool io_poll_remove_all(struct io_ring_ctx *ctx,
 	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;
 
@@ -5708,6 +5709,7 @@ static __cold bool io_poll_remove_all(struct io_ring_ctx *ctx,
 				posted += io_poll_remove_one(req);
 		}
 	}
+	spin_unlock_irq(&ctx->timeout_lock);
 	spin_unlock(&ctx->completion_lock);
 
 	if (posted)
@@ -9568,9 +9570,9 @@ static bool io_cancel_task_cb(struct io_wq_work *work, void *data)
 		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);
 	}
@@ -9585,12 +9587,14 @@ static __cold bool io_cancel_defer_files(struct io_ring_ctx *ctx,
 	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;
-- 
2.33.1

Re: [PATCH 1/1] io_uring: correct link-list traversal locking

[Jens Axboe]

On Tue, 23 Nov 2021 01:45:35 +0000, Pavel Begunkov wrote:
> 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.
> 
> 

Applied, thanks!

[1/1] io_uring: correct link-list traversal locking
      commit: 674ee8e1b4a41d2fdffc885c55350c3fbb38c22a

Best regards,
-- 
Jens Axboe