linux-kernel - Re: [RESEND][PATCH] 9p: add write-cache support to loose cache mode

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: <20070213161607.0ca21ea4.akpm@linux-foundation.org>
Date:	Tue, 13 Feb 2007 16:16:07 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Eric Van Hensbergen <ericvh@...il.com>
Cc:	linux-kernel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
	ericvh@...il.com
Subject: Re: [RESEND][PATCH] 9p: add write-cache support to loose cache mode

> On Tue, 13 Feb 2007 17:55:31 -0600 Eric Van Hensbergen <ericvh@...il.com> wrote:
> +int v9fs_prepare_write(struct file *file, struct page *page,
> +		       unsigned from, unsigned to)
> +{
> +	if (!PageUptodate(page)) {
> +		if (to - from != PAGE_CACHE_SIZE) {
> +			void *kaddr = kmap_atomic(page, KM_USER0);
> +			memset(kaddr, 0, from);
> +			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
> +			flush_dcache_page(page);
> +			kunmap_atomic(kaddr, KM_USER0);
> +		}
> +		SetPageUptodate(page);
> +	}

This will mark the page uptodate while the piece between `to' and `from' is
uninitialised.  A concurrent pagefault can come in and permit a read of
that uninitialised data.  Because filemap_nopage() doesn't lock the page if
it is uptodate.
-
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/