linux-kernel - Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler

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: <20120104151632.05e6b3b0.akpm@linux-foundation.org>
Date:	Wed, 4 Jan 2012 15:16:32 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Hillf Danton <dhillf@...il.com>
Cc:	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault
 handler

On Fri, 23 Dec 2011 21:00:41 +0800
Hillf Danton <dhillf@...il.com> wrote:

> Page mapcount should be updated only if we are sure that the page ends
> up in the page table otherwise we would leak if we couldn't COW due to
> reservations or if idx is out of bounds.

It would be much nicer if we could run vma_needs_reservation() before
even looking up or allocating the page.

And afaict the interface is set up to do that: you run
vma_needs_reservation() before allocating the page and then
vma_commit_reservation() afterwards.

But hugetlb_no_page() and hugetlb_fault() appear to have forgotten to
run vma_commit_reservation() altogether.  Why isn't this as busted as
it appears to be?
--
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/