From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Collingbourne <pcc@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Dave Martin <Dave.Martin@arm.com>, Will Deacon <will@kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Alistair Delva <adelva@google.com>,
Lokesh Gidra <lokeshgidra@google.com>,
William McVicker <willmcvicker@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Mitch Phillips <mitchp@google.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-mm@kvack.org
Subject: Re: [PATCH] userfaultfd: preserve user-supplied address tag in struct uffd_msg
Date: Wed, 30 Jun 2021 16:08:31 -0700 [thread overview]
Message-ID: <20210630160831.cf30a5cfa1df524aed42f3bd@linux-foundation.org> (raw)
In-Reply-To: <20210629012010.1948546-1-pcc@google.com>
On Mon, 28 Jun 2021 18:20:10 -0700 Peter Collingbourne <pcc@google.com> wrote:
> If a user program uses userfaultfd on ranges of heap memory, it may
> end up passing a tagged pointer to the kernel in the range.start
> field of the UFFDIO_REGISTER ioctl. This can happen when using an
> MTE-capable allocator, or on Android if using the Tagged Pointers
> feature for MTE readiness [1].
>
> When a fault subsequently occurs, the tag is stripped from the fault
> address returned to the application in the fault.address field
> of struct uffd_msg. However, from the application's perspective,
> the tagged address *is* the memory address, so if the application
> is unaware of memory tags, it may get confused by receiving an
> address that is, from its point of view, outside of the bounds of the
> allocation. We observed this behavior in the kselftest for userfaultfd
> [2] but other applications could have the same problem.
>
> Fix this by remembering which tag was used to originally register the
> userfaultfd and passing that tag back in fault.address. In a future
> enhancement, we may want to pass back the original fault address,
> but like SA_EXPOSE_TAGBITS, this should be guarded by a flag.
Do we have a Fixes: for this?
Is a -stable backport warranted?
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next prev parent reply other threads:[~2021-06-30 23:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-29 1:20 [PATCH] userfaultfd: preserve user-supplied address tag in struct uffd_msg Peter Collingbourne
2021-06-30 23:08 ` Andrew Morton [this message]
2021-06-30 23:29 ` Peter Collingbourne
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