linux-kernel - Re: [PATCH] cgroup: Fix root_count when mount fails due to busy subsystem

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20090123175028.GC16348@elte.hu>
Date:	Fri, 23 Jan 2009 18:50:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Paul Menage <menage@...gle.com>
Cc:	akpm@...ux-foundation.org, serue@...ibm.com,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] cgroup: Fix root_count when mount fails due to busy
	subsystem


* Paul Menage <menage@...gle.com> wrote:

> On Fri, Jan 23, 2009 at 2:22 AM, Ingo Molnar <mingo@...e.hu> wrote:
> >> --- a/kernel/cgroup.c
> >> +++ b/kernel/cgroup.c
> >> @@ -1115,8 +1115,10 @@ static void cgroup_kill_sb(struct super_block *sb) {
> >>       }
> >>       write_unlock(&css_set_lock);
> >>
> >> -     list_del(&root->root_list);
> >> -     root_count--;
> >> +     if (!list_empty(&root->root_list)) {
> >> +             list_del(&root->root_list);
> >> +             root_count--;
> >> +     }
> >
> > That's ugly. It is _much_ cleaner to always keep the link head consistent
> > - i.e. initialize it with INIT_LIST_HEAD()
> 
> It is initialized with INIT_LIST_HEAD().
> 
> > and then remove from it via
> > list_del_init().
> 
> There's not much point doing list_del_init() rather than list_del()
> here since we're about to delete the root.
> 
> >
> > That way the error path will do the right thing automatically, and there's
> > no need for that ugly "if !list_empty" construct either.
> 
> The important part here is avoiding decrementing root_count.

that should be done via proper placement of err_* labels. An assymetric 
exit path like the one you did is always the sign of bad code structure.

	Ingo
--
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/