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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Fri, 29 Jun 2018 17:19:36 +0200
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Subject: Re: [PATCH v4 0/7] arm64: untag user pointers passed to the kernel
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>
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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