Re: [PATCH v4 0/7] arm64: untag user pointers passed to the kernel

From: Andrey Konovalov <andreyknvl@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Kees Cook <keescook@chromium.org>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Shuah Khan <shuah@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-doc@vger.kernel.org,
	Linux Memory Management List <linux-mm@kvack.org>,
	linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Chintan Pandya <cpandya@codeaurora.org>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Evgeniy Stepanov <eugenis@google.com>
Subject: Re: [PATCH v4 0/7] arm64: untag user pointers passed to the kernel
Date: Fri, 29 Jun 2018 17:19:36 +0200	[thread overview]
Message-ID: <CAAeHK+x4jaN9w8O+hYJ0835Ln=rQ8VT1=ZrKLNsBOT92+iOwdQ@mail.gmail.com> (raw)
In-Reply-To: <CAAeHK+wJbbCZd+-X=9oeJgsqQJiq8h+Aagz3SQMPaAzCD+pvFw@mail.gmail.com>

a bunch of compat
a bunch of ioctl that use ptr to stored ints

ipc/shm.c:1355
ipc/shm.c:1566

mm/process_vm_access.c:178:20
mm/process_vm_access.c:180:19
substraction => harmless

mm/process_vm_access.c:221:4
?

mm/memory.c:4679:14
should be __user pointer

fs/fuse/file.c:1256:9
?

kernel/kthread.c:73:9
?

mm/migrate.c:1586:10
mm/migrate.c:1660:24

lib/iov_iter.c
???

kernel/futex.c:502
uses user addr as key

kernel/futex.c:730
gup, fixed

lib/strncpy_from_user.c:110:13
fixed?

lib/strnlen_user.c:112
fixed?

fs/readdir.c:369
???

On Thu, Jun 28, 2018 at 9:30 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> On Wed, Jun 27, 2018 at 5:05 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> On Tue, Jun 26, 2018 at 7:29 PM, Catalin Marinas
>> <catalin.marinas@arm.com> wrote:
>>> 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.
>
> I've prototyped a checker on top of clang static analyzer (initially
> looked at sparse, but couldn't find any documentation or examples).
> The results are here [1], search for "warning: user pointer cast".
> Sharing in case anybody wants to take a look, will look at them myself
> tomorrow.
>
> [1] https://gist.github.com/xairy/433edd5c86456a64026247cb2fef2115