From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Tal Zussman <tz2294@columbia.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Peter Xu <peterx@redhat.com>,
David Hildenbrand <david@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2 1/4] userfaultfd: correctly prevent registering VM_DROPPABLE regions
Date: Sat, 7 Jun 2025 08:40:14 -0600 [thread overview]
Message-ID: <aERPTlivjt16jCVH@zx2c4.com> (raw)
In-Reply-To: <20250607-uffd-fixes-v2-1-339dafe9a2fe@columbia.edu>
On Sat, Jun 07, 2025 at 02:40:00AM -0400, Tal Zussman wrote:
> vma_can_userfault() masks off non-userfaultfd VM flags from vm_flags.
> The vm_flags & VM_DROPPABLE test will then always be false, incorrectly
> allowing VM_DROPPABLE regions to be registered with userfaultfd.
>
> Additionally, vm_flags is not guaranteed to correspond to the actual
> VMA's flags. Fix this test by checking the VMA's flags directly.
>
> Link: https://lore.kernel.org/linux-mm/5a875a3a-2243-4eab-856f-bc53ccfec3ea@redhat.com/
> Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings")
> Acked-by: David Hildenbrand <david@redhat.com>
> Acked-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Nice catch and thanks for fixing this.
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
next prev parent reply other threads:[~2025-06-07 14:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-07 6:39 [PATCH v2 0/4] mm: userfaultfd: assorted fixes and cleanups Tal Zussman
2025-06-07 6:40 ` [PATCH v2 1/4] userfaultfd: correctly prevent registering VM_DROPPABLE regions Tal Zussman
2025-06-07 14:40 ` Jason A. Donenfeld [this message]
2025-06-07 22:04 ` Andrew Morton
2025-06-09 15:02 ` Peter Xu
2025-06-07 6:40 ` [PATCH v2 2/4] userfaultfd: remove (VM_)BUG_ON()s Tal Zussman
2025-06-10 7:26 ` David Hildenbrand
2025-06-17 23:10 ` Tal Zussman
2025-06-23 15:18 ` David Hildenbrand
2025-06-10 13:11 ` Peter Xu
2025-06-10 13:17 ` David Hildenbrand
2025-06-07 6:40 ` [PATCH v2 3/4] userfaultfd: prevent unregistering VMAs through a different userfaultfd Tal Zussman
2025-06-10 7:30 ` David Hildenbrand
2025-06-17 20:50 ` Tal Zussman
2025-06-07 6:40 ` [PATCH v2 4/4] userfaultfd: remove UFFD_CLOEXEC, UFFD_NONBLOCK, and UFFD_FLAGS_SET Tal Zussman
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