linux-kernel - Re: [patch] IA64: suppress return value of down_trylock() in salinfo_work_to

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]

Message-ID: <20080803024327.GE26461@parisc-linux.org>
Date:	Sat, 2 Aug 2008 20:43:28 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Keith Owens <kaos@....com.au>
Cc:	Simon Horman <horms@...ge.net.au>, linux-ia64@...r.kernel.org,
	linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>
Subject: Re: [patch] IA64: suppress return value of down_trylock() in salinfo_work_to_do()

On Sun, Aug 03, 2008 at 12:08:08PM +1000, Keith Owens wrote:
> >task A acquires sem
> >
> >task B tries to acquire the sem, fails
> >task B releases the sem that it didn't acquire
> >
> >task A releases the sem, falls down, goes boom?
> 
> Cannot happen.  See the comment above the function:
> 
>   This routine must be called with data_saved_lock held, to make the down/up
>   operation atomic

... that requres one to know that salinfo_work_to_do() is the only place
which calls up() (and it always calls down_trylock first).  This is a
really creative misuse of semaphores.

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
--
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/