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Message-ID: <CAHk-=wiKm3QjM1_XwWNW8P8drW6s0ZeANm7VKy_1c7WH6RSp3g@mail.gmail.com>
Date: Tue, 9 Aug 2022 11:48:25 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Peter Xu <peterx@...hat.com>, Hugh Dickins <hughd@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
John Hubbard <jhubbard@...dia.com>,
Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v1] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW
On Mon, Aug 8, 2022 at 12:32 AM David Hildenbrand <david@...hat.com> wrote:
>
> For example, a write() via /proc/self/mem to a uffd-wp-protected range has
> to fail instead of silently granting write access and bypassing the
> userspace fault handler.
This, btw, just makes me go "uffd-wp is broken garbage" once more.
It also makes me go "if uffd-wp can disallow ptrace writes, then why
doesn't regular write protect do it"?
IOW, I don't think the patch is wrong (apart from the VM_BUG_ON's that
absolutely must go away), but I get the strong feelign that we instead
should try to get rid of FOLL_FORCE entirely.
If some other user action can stop FOLL_FORCE anyway, then why do we
support it at all?
Linus
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