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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH] io_uring: Fix LINK_TIMEOUT checks
Date: Thu, 14 Nov 2019 17:12:04 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 11/14/19 2:25 PM, Jens Axboe wrote:
> On 11/14/19 2:20 PM, Pavel Begunkov wrote:
>> If IORING_OP_LINK_TIMEOUT request is a head of a link or an individual
>> request, pass it further through the submission path, where it will
>> eventually fail in __io_submit_sqe(). So respecting links and drains.
>>
>> The case, which is really need to be checked, is if a
>> IORING_OP_LINK_TIMEOUT request is 3rd or later in a link, that is
>> invalid from the user API perspective (judging by the code). Moreover,
>> put/free and friends will try to io_link_cancel_timeout() such request,
>> even though it wasn't initialised.
> 
> Care to add a test case for these to liburings test/link-timeout.c?

Wrote some test cases, I think that io_req_link_next() is just wrong.
The below should correct it. We shouldn't loop here at all, just find
the first one. That'll start that guy, sequence will continue, etc.

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5ad652fa24b8..3230da399681 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -858,7 +858,7 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
 	 * safe side.
 	 */
 	nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb, list);
-	while (nxt) {
+	if (nxt) {
 		list_del_init(&nxt->list);
 		if (!list_empty(&req->link_list)) {
 			INIT_LIST_HEAD(&nxt->link_list);
@@ -876,12 +876,12 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
 			/* we dropped this link, get next */
 			nxt = list_first_entry_or_null(&req->link_list,
 							struct io_kiocb, list);
-		} else if (nxtptr && io_wq_current_is_worker()) {
-			*nxtptr = nxt;
-			break;
-		} else {
-			io_queue_async_work(nxt);
-			break;
+		}
+		if (nxt) {
+			if (nxtptr && io_wq_current_is_worker())
+				*nxtptr = nxt;
+			else
+				io_queue_async_work(nxt);
 		}
 	}
 
-- 
Jens Axboe


  parent reply	other threads:[~2019-11-15  0:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-14 21:20 [PATCH] io_uring: Fix LINK_TIMEOUT checks Pavel Begunkov
2019-11-14 21:25 ` Jens Axboe
2019-11-14 21:31   ` Pavel Begunkov
2019-11-15  0:12   ` Jens Axboe [this message]
2019-11-15  2:36     ` Jens Axboe
2019-11-15  3:22       ` Jens Axboe

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