linux-kernel - Re: [PATCH] mm: fix lazy vmap purging (use-after-free error)

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]

Date:	Mon, 23 Feb 2009 18:20:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Vegard Nossum <vegard.nossum@...il.com>, stable@...nel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: fix lazy vmap purging (use-after-free error)


* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> On Tue, Feb 24, 2009 at 12:29:36AM +1100, Nick Piggin wrote:
> > On Monday 23 February 2009 16:17:09 Paul E. McKenney wrote:
> > 
> > > The boot CPU runs in the context of its idle thread during boot-up.
> > > During this time, idle_cpu(0) will always return nonzero, which will
> > > fool Classic and Hierarchical RCU into deciding that a large chunk of
> > > the boot-up sequence is a big long quiescent state.  This in turn causes
> > > RCU to prematurely end grace periods during this time.
> > >
> > > This patch creates a new global variable that is set to 1 just before
> > > the boot CPU first enters the scheduler, after which the idle task
> > > really is idle.
> > 
> > Nice work all (btw. if this patch goes in rather than using system_state,
> > then please make the variable __read_mostly).
> 
> Hmmm...  I misread this and made system_state be 
> __read_mostly.  Let me know if this is bad, easy to fix if 
> needed.

no, it's the right thing to do. I'd not be surprised if we were 
already running into it as a performance problem - a number of 
common things check this flag.

	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/