linux-kernel - Re: [RFC] coccicheck: add a test for repeat memory fetches

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAGXu5jJ55j1r3H2NP8P4Tv4kqu+DZbj+Q6eor6mUcX8eRj4NTQ@mail.gmail.com>
Date:   Tue, 10 Jan 2017 16:04:06 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     cocci@...teme.lip6.fr, Pengfei Wang <wpengfeinudt@...il.com>,
        Vaishali Thakkar <vthakkar1994@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] coccicheck: add a test for repeat memory fetches

On Tue, Jan 10, 2017 at 1:14 PM, Julia Lawall <julia.lawall@...6.fr> wrote:
> OK, I have the impression that what you are looking for is the following,
> that currently does not seem to work well. Still maybe it gives an idea.
>
> The basic pattern is the following sequence:
>
> 1. copy_from_user
> 2. test on a field of the copied value
> 3. another copy_from_user
> 4. a use of the same field as tested in step 2 from the structure obtained
> by the second copy_from_user or a function call with the structure as an
> argument

This looks pretty good!

> In the case where the second copy_from_user stores the result in a
> pointer, then a return with no reference of the tested field is also a
> concern, unless, the pointer was already kfreed.

I think sequence "2" above missing just looking at a direct value,
like if instead of a field it was a u32. Also, should binop include
"=="?

And we need to add back in get_user() too... hmmm

-Kees

-- 
Kees Cook
Nexus Security