linux-kernel - Subject: [PATCH] APM: fix deadlock in APM_IOC

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]

Date:	Sun, 1 Apr 2012 20:19:30 +1000
From:	NeilBrown <neilb@...e.de>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Subject: [PATCH] APM: fix deadlock in APM_IOC_SUSPEND ioctl

I found the Xorg server on my ARM device stuck in the 'msleep()' loop
in apm_ioctl.

I suspect it had attempted suspend immediately after resuming and lost
a race.
During that msleep(10);, a new suspend cycle must have started and
changed ->suspend_state to SUSPEND_PENDING, so it was never seen to
be SUSPEND_DONE and the loop could never exited.  It would have moved on
to SUSPEND_ACKTO but never been able to reach SUSPEND_DONE.

So change the loop to only run while SUSPEND_ACKED rather than until
SUSPEND_DONE.  This is much safer.

Signed-off-by: NeilBrown <neilb@...e.de>

diff --git a/drivers/char/apm-emulation.c b/drivers/char/apm-emulation.c
index f4837a8..6005c5c 100644
--- a/drivers/char/apm-emulation.c
+++ b/drivers/char/apm-emulation.c
@@ -302,7 +302,7 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg)
 			 * anything critical, chill a bit on each iteration.
 			 */
 			while (wait_event_freezable(apm_suspend_waitqueue,
-					as->suspend_state == SUSPEND_DONE))
+					as->suspend_state != SUSPEND_ACKED))
 				msleep(10);
 			break;
 		case SUSPEND_ACKTO:

Download attachment "signature.asc" of type "application/pgp-signature" (829 bytes)