From: Catalin Marinas <catalin.marinas@arm.com>
To: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
Mark Rutland <Mark.Rutland@arm.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
Will Deacon <Will.Deacon@arm.com>,
Kostya Serebryany <kcc@google.com>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
Chintan Pandya <cpandya@codeaurora.org>,
Shuah Khan <shuah@kernel.org>, Ingo Molnar <mingo@kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
Jacob Bramley <Jacob.Bramley@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
Evgeniy Stepanov <eugenis@google.com>,
Kees Cook <keescook@chromium.org>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Al Viro <viro@zeniv.linux.org.uk>, nd <nd@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Lee Smith <Lee.Smith@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Robin Murphy <Robin.Murphy@arm.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v4 0/7] arm64: untag user pointers passed to the kernel
Date: Wed, 27 Jun 2018 18:17:58 +0100 [thread overview]
Message-ID: <20180627171757.amucnh5znld45cpc@armageddon.cambridge.arm.com> (raw)
In-Reply-To: <0cef1643-a523-98e7-95e2-9ec595137642@arm.com>
On Wed, Jun 27, 2018 at 04:08:09PM +0100, Ramana Radhakrishnan wrote:
> On 27/06/2018 16:05, Andrey Konovalov wrote:
> > On Tue, Jun 26, 2018 at 7:29 PM, Catalin Marinas
> > <catalin.marinas@arm.com> wrote:
> >> On Tue, Jun 26, 2018 at 02:47:50PM +0200, Andrey Konovalov wrote:
> >>> On Wed, Jun 20, 2018 at 5:24 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> >>>> arm64 has a feature called Top Byte Ignore, which allows to embed pointer
> >>>> tags into the top byte of each pointer. Userspace programs (such as
> >>>> HWASan, a memory debugging tool [1]) might use this feature and pass
> >>>> tagged user pointers to the kernel through syscalls or other interfaces.
> >>>>
> >>>> This patch makes a few of the kernel interfaces accept tagged user
> >>>> pointers. The kernel is already able to handle user faults with tagged
> >>>> pointers and has the untagged_addr macro, which this patchset reuses.
> >>>>
> >>>> We're not trying to cover all possible ways the kernel accepts user
> >>>> pointers in one patchset, so this one should be considered as a start.
> >>>>
> >>>> Thanks!
> >>>>
> >>>> [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
> >>>
> >>> Is there anything I should do to move forward with this?
> >>>
> >>> I've received zero replies to this patch set (v3 and v4) over the last
> >>> month.
> >>
> >> The patches in this series look fine but my concern is that they are not
> >> sufficient and we don't have (yet?) a way to identify where such
> >> annotations are required. You even say in patch 6 that this is "some
> >> initial work for supporting non-zero address tags passed to the kernel".
> >> Unfortunately, merging (or relaxing) an ABI without a clear picture is
> >> not really feasible.
> >>
> >> While I support this work, as a maintainer I'd like to understand
> >> whether we'd be in a continuous chase of ABI breaks with every kernel
> >> release or we have a better way to identify potential issues. Is there
> >> any way to statically analyse conversions from __user ptr to long for
> >> example? Or, could we get the compiler to do this for us?
> >
> > OK, got it, I'll try to figure out a way to find these conversions.
>
> This sounds like the kind of thing we should be able to get sparse to do
> already, no ? It's been many years since I last looked at it but I
> thought sparse was the tool of choice in the kernel to do this kind of
> checking.
sparse is indeed an option. The current implementation doesn't warn on
an explicit cast from (void __user *) to (unsigned long) since that's a
valid thing in the kernel. I couldn't figure out if there's any other
__attribute__ that could be used to warn of such conversion.
--
Catalin
next prev parent reply other threads:[~2018-06-27 17:18 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-20 15:24 [PATCH v4 0/7] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 1/7] arm64: add type casts to untagged_addr macro Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 2/7] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 3/7] arm64: untag user addresses in access_ok and __uaccess_mask_ptr Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 4/7] mm, arm64: untag user addresses in mm/gup.c Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 5/7] lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 6/7] arm64: update Documentation/arm64/tagged-pointers.txt Andrey Konovalov
2018-06-20 15:24 ` [PATCH v4 7/7] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2018-06-26 12:47 ` [PATCH v4 0/7] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-06-26 17:29 ` Catalin Marinas
2018-06-27 15:05 ` Andrey Konovalov
2018-06-27 15:08 ` Ramana Radhakrishnan
2018-06-27 17:17 ` Catalin Marinas [this message]
2018-06-28 6:17 ` Luc Van Oostenryck
2018-06-28 10:27 ` Catalin Marinas
2018-06-28 10:46 ` Luc Van Oostenryck
2018-06-28 14:48 ` Catalin Marinas
2018-06-28 15:28 ` Luc Van Oostenryck
2018-06-29 15:27 ` David Laight
2018-06-28 23:21 ` [PATCH] sparse: stricter warning for explicit cast to ulong Luc Van Oostenryck
2018-06-28 19:30 ` [PATCH v4 0/7] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-06-29 15:19 ` Andrey Konovalov
2018-06-29 15:20 ` Andrey Konovalov
2018-07-16 11:25 ` Andrey Konovalov
2018-07-31 13:23 ` Andrey Konovalov
2018-08-01 17:42 ` Catalin Marinas
2018-08-02 15:00 ` Andrey Konovalov
2018-08-03 14:59 ` Andrey Konovalov
2018-08-03 15:09 ` Greg Kroah-Hartman
2018-08-03 16:43 ` Matthew Wilcox
2018-08-03 16:54 ` Andrey Konovalov
2018-08-06 19:12 ` Luc Van Oostenryck
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