linux-kernel - Re: [PATCH] sys_remap_file_pages: fix ->vm

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:	Wed, 6 Feb 2008 20:13:04 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Miklos Szeredi <mszeredi@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	William Lee Irwin III <wli@...omorphy.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Matt Helsley <matthltc@...ibm.com>
Subject: Re: [PATCH] sys_remap_file_pages: fix ->vm_file accounting

[ removed stable ]

On Sun, 3 Feb 2008, Oleg Nesterov wrote:
> Off-topic question to all. sys_remap_file_pages() doesn't work with
> shared readonly mappings, why?

Slight correction: it works with shared readonly mappings, doesn't
it, so long as the mmap'ed file was opened for reading and writing?

> IOW, why it checks VM_SHARED but not VM_MAYSHARE?

My guess has always been that it was just a misunderstanding of how
those VM_ flags end up working: assume so unless Ingo corrects me.

By the time I realized that oddity, we'd been driven into several
tiresome corners by the very existence of sys_remap_file_pages.
So whereas my usual instinct would have been to relax the restriction
and generalize, in its case I wanted to hold on to every restriction
we had.

sys_remap_file_pages does serve a useful purpose; but it subverts
vma principles, and has therefore caused us grief repeatedly.

Hugh
--
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/