From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Mike Rapoport <rppt@kernel.org>,
Jordy Zomer <jordy@jordyzomer.github.io>,
linux-mm@kvack.org, Dmitry Vyukov <dvyukov@google.com>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
David Hildenbrand <david@redhat.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] mm/secretmem: Avoid letting secretmem_users drop to zero
Date: Thu, 21 Oct 2021 19:53:11 -0700 [thread overview]
Message-ID: <20211021195311.6058b90f573641542605dae4@linux-foundation.org> (raw)
In-Reply-To: <20211021154046.880251-1-keescook@chromium.org>
On Thu, 21 Oct 2021 08:40:46 -0700 Kees Cook <keescook@chromium.org> wrote:
> Quoting Dmitry: "refcount_inc() needs to be done before fd_install().
> After fd_install() finishes, the fd can be used by userspace and we can
> have secret data in memory before the refcount_inc().
>
> A straightforward mis-use where a user will predict the returned fd
> in another thread before the syscall returns and will use it to store
> secret data is somewhat dubious because such a user just shoots themself
> in the foot.
>
> But a more interesting mis-use would be to close the predicted fd and
> decrement the refcount before the corresponding refcount_inc, this way
> one can briefly drop the refcount to zero while there are other users
> of secretmem."
>
> Move fd_install() after refcount_inc().
I added cc:stable. Or doesn't the benefit/risk ratio justify that?
next prev parent reply other threads:[~2021-10-22 2:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 15:40 Kees Cook
2021-10-21 15:48 ` Dmitry Vyukov
2021-10-21 15:50 ` David Hildenbrand
2021-10-21 16:47 ` Jordy Zomer
2021-10-22 2:53 ` Andrew Morton [this message]
2021-10-22 3:39 ` Kees Cook
2021-10-22 7:09 ` Mike Rapoport
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