Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode

From	Thomas Garnier <thgarnie@google.com>
Newsgroups	linux.kernel
Subject	Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode
Date	2017-05-08 22:00 +0200
Message-ID	<tEWZ3-8eF-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <tDTJT-7Nn-3@gated-at.bofh.it> <tELqV-VP-1@gated-at.bofh.it> <tELKi-14K-19@gated-at.bofh.it> <tESLN-5F6-35@gated-at.bofh.it> <tESLN-5F6-43@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, May 8, 2017 at 8:26 AM, Kees Cook <keescook@chromium.org> wrote:
> On Mon, May 8, 2017 at 8:22 AM, Daniel Micay <danielmicay@gmail.com> wrote:
>> On Mon, 2017-05-08 at 09:52 +0200, Ingo Molnar wrote:
>>>
>>> ... it's just not usable in that form for a regular maintenance flow.
>>>
>>> So what would be more useful is to add a specific Sparse check that
>>> only checks
>>> KERNEL_DS, to add it as a regular (.config driven) build option and
>>> make sure the
>>> kernel build has zero warnings.
>>>
>>> From that point on we can declare that this kind of bug won't occur
>>> anymore, if
>>> the Sparse implementation of the check is correct.
>>>
>>> But there's a (big) problem with that development model: Sparse is not
>>> part of the
>>> kernel tree and adding a feature to it while making the kernel depend
>>> on that
>>> brand new feature is a logistical nightmare. The overhead is quite
>>> similar to
>>> adding new features to a compiler - it happens at a glacial pace and
>>> is only done
>>> for major features really, at considerable expense. I don't think this
>>> is an
>>> adequate model for 'extended syntax checking' of the kernel,
>>> especially when it
>>> comes to correctness that has such obvious security impact.
>>>
>>> Thanks,
>>>
>>>       Ingo
>>
>> There's the option of using GCC plugins now that the infrastructure was
>> upstreamed from grsecurity. It can be used as part of the regular build
>> process and as long as the analysis is pretty simple it shouldn't hurt
>> compile time much.
>
> Well, and that the situation may arise due to memory corruption, not
> from poorly-matched set_fs() calls, which static analysis won't help
> solve. We need to catch this bad kernel state because it is a very bad
> state to run in.

Of course, I agree with Kees points on this and previous emails.

A static analysis solution is hard to scale across functions and build
time can suffer. I don't think the coverage will be good enough to
consider this change and static analysis as similar.

>
> -Kees
>
> --
> Kees Cook
> Pixel Security



-- 
Thomas

Thread

[PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode Thomas Garnier <thgarnie@google.com> - 2017-04-28 17:40 +0200
  Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode Thomas Garnier <thgarnie@google.com> - 2017-05-06 00:20 +0200
    Re: [PATCH v9 1/4] syscalls: Verify address limit before returning  to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-08 09:40 +0200
      Re: [PATCH v9 1/4] syscalls: Verify address limit before returning  to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-08 10:00 +0200
        Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Daniel Micay <danielmicay@gmail.com> - 2017-05-08 17:30 +0200
          Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-08 17:30 +0200
            Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Thomas Garnier <thgarnie@google.com> - 2017-05-08 22:00 +0200
            Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-09 09:00 +0200
              Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Greg KH <greg@kroah.com> - 2017-05-09 13:20 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Thomas Garnier <thgarnie@google.com> - 2017-05-09 16:40 +0200
              Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-09 18:40 +0200
      Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Greg KH <greg@kroah.com> - 2017-05-08 14:50 +0200
        Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-09 08:50 +0200
          Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-09 11:00 +0200
            Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Andy Lutomirski <luto@kernel.org> - 2017-05-09 15:10 +0200
              Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-09 15:10 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-09 18:10 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-09 19:00 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Andy Lutomirski <luto@amacapital.net> - 2017-05-10 01:00 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-10 01:40 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Andy Lutomirski <luto@kernel.org> - 2017-05-10 04:10 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:20 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Borislav Petkov <bp@alien8.de> - 2017-05-11 13:30 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 08:50 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 04:20 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 04:50 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 05:20 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 05:30 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 05:50 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:00 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:00 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 09:30 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:40 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:00 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Arnd Bergmann <arnd@arndb.de> - 2017-05-10 09:30 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 09:40 +0200
              Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Brian Gerst <brgerst@gmail.com> - 2017-05-09 18:10 +0200
              Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Arnd Bergmann <arnd@arndb.de> - 2017-05-10 09:40 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-10 10:10 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Christoph Hellwig <hch@infradead.org> - 2017-05-10 10:20 +0200
                Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address  limit before returning to user-mode Andy Lutomirski <luto@kernel.org> - 2017-05-11 02:20 +0200
      Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-08 15:20 +0200
        Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode Jann Horn <jannh@google.com> - 2017-05-08 16:10 +0200
          Re: [PATCH v9 1/4] syscalls: Verify address limit before returning  to user-mode Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-08 22:50 +0200
        Re: [PATCH v9 1/4] syscalls: Verify address limit before returning  to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-08 16:10 +0200
          Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode Kees Cook <keescook@chromium.org> - 2017-05-08 17:30 +0200
            Re: [PATCH v9 1/4] syscalls: Verify address limit before returning  to user-mode Ingo Molnar <mingo@kernel.org> - 2017-05-09 08:40 +0200

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