linux-kernel - Re: [PATCH 2.6.36 1/1 RESEND] kernel SPIN_LOCK_UNLOCKED changed to __SPIN_LOCK

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] [day] [month] [year] [list]

Date:	Mon, 15 Nov 2010 10:06:06 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Atul Sowani <sowani@...il.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, alan@...ux.intel.com,
	ralf@...ux-mips.org
Subject: Re: [PATCH 2.6.36 1/1 RESEND] kernel SPIN_LOCK_UNLOCKED changed to
	__SPIN_LOCK_UNLOCKED()

On Mon, Nov 15, 2010 at 10:44:36AM +0100, Arnd Bergmann wrote:
> On Monday 15 November 2010 10:24:04 Russell King - ARM Linux wrote:
> > This lock is in the percpu data area.  This means that when other CPUs
> > are brought online, and therefore other percpu areas are instantiated,
> > this lock will be mis-initialized (the pointers et.al. will be pointing
> > at the original percpu instance.)
> > 
> > So NAK, this will break.
> 
> I believe right now we only use the argument of __SPIN_LOCK_UNLOCKED
> as an identifier string for lockdep, but not for any pointers, so the
> patch would actually do what was intended, but break if we ever start
> relying on the pointer.
> 
> Maybe we can mangle the argument in some way to make sure it will break
> at build time when that happens, e.g.
> 
>      .lock   = __SPIN_LOCK_UNLOCKED(ipi_data.__lock)
> 
> This would at least let us remove SPIN_LOCK_UNLOCKED.

Or do one of the things I've suggested - one of which I've just completed
the code changes for, and results in this lock going away completely.
It's not a nice idea to have percpu data written to by 'foreign' CPUs.
--
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/