From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
stable@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Peter Xu <peterx@redhat.com>, Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [PATCH v1] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW
Date: Tue, 9 Aug 2022 13:14:49 -0700 [thread overview]
Message-ID: <CAHk-=whg0ddey-LqFAPfZJDXHMjaHJNojAV3q17yvjc6W8QRvQ@mail.gmail.com> (raw)
In-Reply-To: <91e18a2f-c93d-00b8-7c1b-6d8493c3b2d5@redhat.com>
On Tue, Aug 9, 2022 at 1:07 PM David Hildenbrand <david@redhat.com> wrote:
>
> > /* But FOLL_FORCE has no effect on shared mappings */
> > if (vma->vm_flags & MAP_SHARED)
> > return false;
>
> I'd actually rather check for MAP_MAYSHARE here, which is even stronger.
> Thoughts?
Hmm. Adding the test for both is basically free (all those vm_flags
checks end up being a bit mask and compare), so no objections.
For some reason I though VM_SHARED and VM_MAYSHARE end up always being
the same bits, and it was a mistake to make them two bits in the first
place (unlike the read/write/exec bits that can are about mprotect),
But as there are two bits, I'm sure somebody ends up touching one and
not the other.
So yeah, I don't see any downside to just checking both bits.
[ That said, is_cow_mapping() only checks VM_SHARED, so if they are
ever different, that's a potential source of confusion ]
Linus
next prev parent reply other threads:[~2022-08-09 20:15 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-08 7:32 [PATCH v1] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW David Hildenbrand
2022-08-08 16:02 ` David Hildenbrand
2022-08-09 18:27 ` Linus Torvalds
2022-08-09 18:45 ` David Hildenbrand
2022-08-09 18:59 ` Linus Torvalds
2022-08-09 19:07 ` Jason Gunthorpe
2022-08-09 19:21 ` Linus Torvalds
2022-08-09 21:16 ` David Laight
2022-08-11 7:13 ` [PATCH] sched/all: Change BUG_ON() instances to WARN_ON() Ingo Molnar
2022-08-11 20:43 ` Linus Torvalds
2022-08-11 21:28 ` Matthew Wilcox
2022-08-11 23:22 ` Jason Gunthorpe
2022-08-14 1:10 ` John Hubbard
2022-08-12 9:29 ` [PATCH v2] sched/all: Change all BUG_ON() instances in the scheduler to WARN_ON_ONCE() Ingo Molnar
[not found] ` <20220815144143.zjsiamw5y22bvgki@suse.de>
2022-08-15 22:12 ` John Hubbard
2022-08-21 11:28 ` Ingo Molnar
2022-08-09 18:40 ` [PATCH v1] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW Linus Torvalds
2022-08-09 18:48 ` Jason Gunthorpe
2022-08-09 18:53 ` David Hildenbrand
2022-08-09 19:07 ` Linus Torvalds
2022-08-09 19:20 ` David Hildenbrand
2022-08-09 18:48 ` Linus Torvalds
2022-08-09 19:09 ` David Hildenbrand
2022-08-09 20:00 ` Linus Torvalds
2022-08-09 20:06 ` David Hildenbrand
2022-08-09 20:07 ` David Hildenbrand
2022-08-09 20:14 ` Linus Torvalds [this message]
2022-08-09 20:20 ` David Hildenbrand
2022-08-09 20:30 ` Linus Torvalds
2022-08-09 20:38 ` Linus Torvalds
2022-08-09 20:42 ` David Hildenbrand
2022-08-09 20:20 ` Linus Torvalds
2022-08-09 20:23 ` David Hildenbrand
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