From: Andrew Morton <akpm@osdl.org>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: linux-kernel@vger.kernel.org, david@gibson.dropbear.id.au,
torvalds@osdl.org, William Lee Irwin III <wli@holomorphy.com>
Subject: Re: [BUG] hugetlb MAP_PRIVATE mapping vs /dev/zero
Date: Thu, 1 Jul 2004 14:55:41 -0700 [thread overview]
Message-ID: <20040701145541.0ece2898.akpm@osdl.org> (raw)
In-Reply-To: <40E43BDE.85C5D670@tv-sign.ru>
Oleg Nesterov <oleg@tv-sign.ru> wrote:
>
> Hugetlbfs mmap with MAP_PRIVATE becomes MAP_SHARED
> silently, but vma->vm_flags have no VM_SHARED bit.
> I think it make sense to forbid MAP_PRIVATE in
> hugetlbfs_file_mmap() because it may confuse user
> space applications. But the real bug is that reading
> from /dev/zero into hugetlb will do:
>
> read_zero()
> read_zero_pagealigned()
> if (vma->vm_flags & VM_SHARED)
> break; // OK if MAP_PRIVATE
> zap_page_range();
> zeromap_page_range();
>
> We can fix hugetlbfs_file_mmap() or read_zero_pagealigned()
> or both.
This could break existing applications, yes?
If so, would an appropriate fixup be to coerce private mappings
of hugetlb files into shared ones in-kernel?
next prev parent reply other threads:[~2004-07-01 21:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-01 16:29 Oleg Nesterov
2004-07-01 16:56 ` William Lee Irwin III
2004-07-01 21:55 ` Andrew Morton [this message]
2004-07-02 1:20 ` David Gibson
2004-07-02 2:44 ` William Lee Irwin III
2004-07-02 3:49 ` David Gibson
2004-07-02 4:12 ` David Gibson
2004-07-02 4:21 ` William Lee Irwin III
2004-07-02 12:12 Oleg Nesterov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20040701145541.0ece2898.akpm@osdl.org \
--to=akpm@osdl.org \
--cc=david@gibson.dropbear.id.au \
--cc=linux-kernel@vger.kernel.org \
--cc=oleg@tv-sign.ru \
--cc=torvalds@osdl.org \
--cc=wli@holomorphy.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
Powered by JetHome