linux-kernel - [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070419065404.GB1782@ff.dom.local>
Date:	Thu, 19 Apr 2007 08:54:04 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work

Hi,

IMHO cancel_rearming_delayed_work is dangerous place:

- it assumes a work function always rearms (with no exception),
which probably isn't explained enough now (but anyway should
be checked in such loops);

- probably possible (theoretical) scenario: a few work
functions rearm themselves with very short, equal times;
before flush_workqueue ends, their timers are already
fired, so cancel_delayed_work has nothing to do.

Maybe this patch could check, if I'm not dreaming...

PS: of course the counter value below is a question of taste

Signed-off-by: Jarek Poplawski <jarkao2@...pl>

---

diff -Nurp 2.6.21-rc6-mm1-/kernel/workqueue.c 2.6.21-rc6-mm1/kernel/workqueue.c
--- 2.6.21-rc6-mm1-/kernel/workqueue.c	2007-04-18 20:07:45.000000000 +0200
+++ 2.6.21-rc6-mm1/kernel/workqueue.c	2007-04-18 20:15:44.000000000 +0200
@@ -557,9 +557,12 @@ void cancel_rearming_delayed_work(struct
 	/* Was it ever queued ? */
 	if (cwq != NULL) {
 		struct workqueue_struct *wq = cwq->wq;
+		int i = 1000;
 
-		while (!cancel_delayed_work(dwork))
+		while (!cancel_delayed_work(dwork)) {
 			flush_workqueue(wq);
+			BUG_ON(!i--);
+		}
 	}
 }
 EXPORT_SYMBOL(cancel_rearming_delayed_work);
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/