linux-kernel - Re: [PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state setting bug in freezer_change

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

Message-ID: <20110829160031.GB8392@redhat.com>
Date:	Mon, 29 Aug 2011 18:00:31 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul Menage <paul@...lmenage.org>,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state
	setting bug in freezer_change_state()

On 08/29, Tejun Heo wrote:
>
> --- work.orig/kernel/cgroup_freezer.c
> +++ work/kernel/cgroup_freezer.c
> @@ -311,14 +311,14 @@ static int freezer_change_state(struct c
>  	if (goal_state == freezer->state)
>  		goto out;
>  
> -	freezer->state = goal_state;
> -
>  	switch (goal_state) {
>  	case CGROUP_THAWED:
> +		freezer->state = CGROUP_THAWED;
>  		atomic_dec(&system_freezing_cnt);
>  		unfreeze_cgroup(cgroup, freezer);
>  		break;
>  	case CGROUP_FROZEN:
> +		freezer->state = CGROUP_FREEZING;

At first glance, this is correct. I'll try to recheck.

But,

>  		atomic_inc(&system_freezing_cnt);

iiuc this becomes wrong... Suppose a user writes "FROZEN" twice,
before freezer->state becomes CGROUP_FROZEN.

I think we should actually fix the "goal_state == freezer->state"
check above.

Oleg.

--
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/