linux-kernel - Re: [PATCH v9 11/12] x86, mpx: cleanup unused bound tables

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]

Date:	Tue, 11 Nov 2014 19:27:37 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave.hansen@...el.com>
cc:	Qiaowei Ren <qiaowei.ren@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-ia64@...r.kernel.org, linux-mips@...ux-mips.org
Subject: Re: [PATCH v9 11/12] x86, mpx: cleanup unused bound tables

On Thu, 6 Nov 2014, Dave Hansen wrote:
> Instead of all of these games with dropping and reacquiring mmap_sem and
> adding other locks, or deferring the work, why don't we just do a
> get_user_pages()?  Something along the lines of:
> 
> while (1) {
> 	ret = cmpxchg(addr)
> 	if (!ret)
> 		break;
> 	if (ret == -EFAULT)
> 		get_user_pages(addr);
> }
> 
> Does anybody see a problem with that?

You want to do that under mmap_sem write held, right? Not a problem per
se, except that you block normal faults for a possibly long time when
the page(s) need to be swapped in.

But yes, this might solve most of the issues at hand. Did not think
about GUP at all :(

Thanks,

	tglx

--
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/