From: Ralf Baechle <ralf@linux-mips.org>
To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: linux-mips@linux-mips.org
Subject: Re: [MIPS] Fix aliasing bug in copy_user_highpage, take 2.
Date: Tue, 16 Oct 2007 17:16:18 +0100 [thread overview]
Message-ID: <20071016161618.GB23986@linux-mips.org> (raw)
In-Reply-To: <20071017.011349.03977690.anemo@mba.ocn.ne.jp>
On Wed, Oct 17, 2007 at 01:13:49AM +0900, Atsushi Nemoto wrote:
> On Tue, 16 Oct 2007 16:38:06 +0100, Ralf Baechle <ralf@linux-mips.org> wrote:
> > > Hmm, setting SetPageDcacheDirty() will not make sure the modified data
> > > flushed before reading via the kernel mapping. The flush_dcache_page()
> > > should be used for such case, shouldn't it?
> >
> > You're right - and the intent is to _not_ flush the page. But we're
> > bringing it into the cache, so we better flush it before it will be mapped
> > to userspace. We want to delay the flush operation.
>
> I see, but I'm afraid of unnecessary flushing might hide another
> bug...
>
> Setting SetPageDcacheDirty() for non-modified page looks a bit
> overkill for me. For example, in copy_user_highpage() we do not flush
> the source page if the page was not mapped to userspace.
kunmap_atomic() is supposed to deal with that.
It doesn't quite on the MIPS implementation so the kernel refuses highmem
with aliasing caches.
Ralf
prev parent reply other threads:[~2007-10-16 16:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <S20036863AbXJOPrf/20071015154735Z+80955@ftp.linux-mips.org>
2007-10-15 17:31 ` [MIPS] Fix aliasing bug in copy_user_highpage, take 2 Atsushi Nemoto
2007-10-15 18:28 ` Ralf Baechle
2007-10-16 15:29 ` Atsushi Nemoto
2007-10-16 15:38 ` Ralf Baechle
2007-10-16 16:13 ` Atsushi Nemoto
2007-10-16 16:16 ` Ralf Baechle [this message]
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