From: Jason Gunthorpe <jgg@ziepe.ca>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Tomasz Figa <tfiga@chromium.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
DRI Development <dri-devel@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
linux-samsung-soc <linux-samsung-soc@vger.kernel.org>
Subject: Re: [PULL] topic/iomem-mmap-vs-gup
Date: Mon, 10 May 2021 12:34:12 -0300 [thread overview]
Message-ID: <20210510153412.GG2047089@ziepe.ca> (raw)
In-Reply-To: <CAKMK7uFfN3p2fE1Xq47nOTtkPY2vm10GMvBaupQ9hgK0rS8sgQ@mail.gmail.com>
On Mon, May 10, 2021 at 04:55:39PM +0200, Daniel Vetter wrote:
> yeah vfio is still broken for the case I care about. I think there's
> also some questions open still about whether kvm really uses
> mmu_notifier in all cases correctly,
IIRC kvm doesn't either.
> > Daniel I suppose we missed this relation to follow_pte(), so I agree
> > that keeping a unsafe_follow_pfn() around is not good.
>
> tbh I never really got the additional issue with the missing write
> checks. That users of follow_pfn (or well follow_pte + immediate lock
> dropping like vfio) don't subscribe to the pte updates in general is
> the bug I'm seeing. That v4l also glosses over the read/write access
> stuff is kinda just the icing on the cake :-) It's pretty well broken
> even if it would check that.
It is just severity. Exploiting the use after free bug is somewhat
harder, exploiting the 'you can write to non-page write protected
memory' bug is not so hard.
Jason
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next prev parent reply other threads:[~2021-05-10 15:36 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-03 19:15 [PULL] topic/iomem-mmap-vs-gup Daniel Vetter
2021-05-06 22:30 ` Linus Torvalds
2021-05-07 15:53 ` Daniel Vetter
2021-05-08 16:46 ` Linus Torvalds
2021-05-10 7:16 ` Daniel Vetter
2021-05-10 7:29 ` Christoph Hellwig
2021-05-17 15:29 ` Daniel Vetter
2021-05-17 22:04 ` Stephen Rothwell
2021-05-10 13:50 ` Jason Gunthorpe
2021-05-10 14:55 ` Daniel Vetter
2021-05-10 15:34 ` Jason Gunthorpe [this message]
2021-05-10 17:57 ` Sean Christopherson
2021-05-10 18:13 ` Paolo Bonzini
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