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 for kexec@lists.infradead.org; Fri, 12 Nov 2021 13:24:03 +0000
Date: Fri, 12 Nov 2021 21:23:26 +0800
From: Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH v1] proc/vmcore: fix clearing user buffer by properly
 using clear_user()
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To: David Hildenbrand <david@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Philipp Rudo <prudo@redhat.com>, kexec@lists.infradead.org, Linux MM <linux-mm@kvack.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>

On 11/12/21 at 10:08am, David Hildenbrand wrote:
> > > "that allows supervisor mode programs to optionally set user-space
> > > memory mappings so that access to those mappings from supervisor mode
> > > will cause a trap. This makes it harder for malicious programs to
> > > "trick" the kernel into using instructions or data from a user-space
> > > program"
> >
> > OK, probably. I thought it's triggered in access_ok(), and tried to
> > figure out why. But seems we should do something to check this in
> > access_ok(), otherwise the logic of clear_user/_clear_user is not so
> > reasonable. Anyway, I have learned it, thanks a lot for digging it out.
> >
> > By the way, I can't open above wiki article, found below commit from
> > hpa. Maybe we can add some into log to tell this, not strong opinin,
> > leave it to you.
> 
> Yes, now that we know the root cause I'll add some more details to the
> patch description and resend -- thanks Baoquan!

Thanks for sending v2.


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