linux-kernel - Re: [PATCH 1/4] asm-generic: uaccess: do not expand args multiple times

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:	Sun, 14 Jun 2009 22:14:39 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mike Frysinger <vapier@...too.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] asm-generic: uaccess: do not expand args multiple times

On Sunday 14 June 2009, Mike Frysinger wrote:
> While it's debatable whether {get,put}_user() should be called with
> arguments that have side effects, macro's should be written safely in the
> first place.  In this case, a slightly off version of put_user() ended up
> causing random userspace corruption and these things aren't trivial to
> track down.
> 
> While some of these conversions aren't strictly necessary, I think it's
> better to do all of them so as to be proactive in people accidently
> screwing it up in the future.

I've tried this and failed. This change adds an endless number of sparse
warnings in put_user and even gcc warnings in get_user. The problem
is that typeof() carries over the 'const' and '__user' modifiers, both
of which prevent you from assigning data to the new pointer that you
constructed.

I'd love to see a way to do this correctly, but this patch won't cut it.

	Arnd <><
--
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/