From: Johannes Weiner <jweiner@redhat.com>
To: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm/huge_memory: Clean up typo when copying user highpage
Date: Wed, 12 Oct 2011 11:56:46 -0400 [thread overview]
Message-ID: <20111012155646.GC6478@redhat.com> (raw)
In-Reply-To: <CAJd=RBBuwmcV8srUyPGnKUp=RPKvsSd+4BbLrh--aHFGC5s7+g@mail.gmail.com>
On Wed, Oct 12, 2011 at 10:39:36PM +0800, Hillf Danton wrote:
> Hi Andrea
>
> When copying user highpage, the PAGE_SHIFT in the third parameter is a typo,
> I think, and is replaced with PAGE_SIZE.
This is a pretty nasty data corruption bug, so 'clean up' might be a
bit of an understatement ;-)
Nice catch.
Would you mind extending the changelog to include a problem
description? Feel free to steal from this:
The THP copy-on-write handler falls back to regular-sized
pages for a huge page replacement upon allocation failure or
if THP has been individually disabled in the target VMA. The
loop responsible for copying page-sized chunks accidentally
uses multiples of PAGE_SHIFT instead of PAGE_SIZE as the byte
offset into the original huge page, though, and the
COW-breaking task ends up with a corrupt copy of the data.
> Signed-off-by: Hillf Danton <dhillf@gmail.com>
Acked-by: Johannes Weiner <jweiner@redhat.com>
> --- a/mm/huge_memory.c Sat Aug 13 11:45:14 2011
> +++ b/mm/huge_memory.c Wed Oct 12 22:26:15 2011
> @@ -829,7 +829,7 @@ static int do_huge_pmd_wp_page_fallback(
>
> for (i = 0; i < HPAGE_PMD_NR; i++) {
> copy_user_highpage(pages[i], page + i,
> - haddr + PAGE_SHIFT*i, vma);
> + haddr + PAGE_SIZE * i, vma);
> __SetPageUptodate(pages[i]);
> cond_resched();
> }
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-10-12 15:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-12 14:39 [PATCH] mm/huge_memory: Clean up typo when copying user highpage Hillf Danton
2011-10-12 15:56 ` Johannes Weiner [this message]
2011-10-12 17:51 ` Andrea Arcangeli
2011-10-12 20:42 ` Andrew Morton
2011-10-12 22:24 ` Andrea Arcangeli
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=20111012155646.GC6478@redhat.com \
--to=jweiner@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dhillf@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/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;
as well as URLs for NNTP newsgroup(s).