linux-kernel - Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.

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: <20100614212150.4dcb1feb.akpm@linux-foundation.org>
Date:	Mon, 14 Jun 2010 21:21:50 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	tytso@....edu, Salman <sqazi@...gle.com>, mingo@...e.hu,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	tytso@...gle.com, torvalds@...ux-foundation.org, walken@...gle.com,
	Chen Liqin <liqin.chen@...plusct.com>,
	Lennox Wu <lennox.wu@...il.com>
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be
 reused immediately.

On Tue, 15 Jun 2010 13:26:08 +1000 Paul Mackerras <paulus@...ba.org> wrote:

> On Mon, Jun 14, 2010 at 06:55:56PM -0700, Andrew Morton wrote:
> 
> > > kernel/sched_clock.c:   if (cmpxchg64(&scd->clock, old_clock, clock) != old_cloc
> > 
> > I guess that'll flush out any stragglers.
> 
> And break most non-x86 32-bit architectures, including 32-bit powerpc.

If CONFIG_SMP=y, yes.  On UP there's a generic implementation
(include/asm-generic/cmpxchg-local.h, include/asm-generic/cmpxchg.h)

> Fortunately that code is only used if CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
> is set, and it looks like only x86 and ia64 set it.
> 

If that happens then the best fix is for those architectures to get
themselves a cmpxchg64().  Unless for some reason it's simply
unimplementable?  Worst case I guess one could use a global spinlock. 
Second-worst-case: hashed spinlocks.
--
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/