RE: [PATCH v3 00/11] mm: Hardened usercopy
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- To: "'Kees Cook'" <keescook@xxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>
- Subject: RE: [PATCH v3 00/11] mm: Hardened usercopy
- From: David Laight <David.Laight@xxxxxxxxxx>
- Date: Wed, 20 Jul 2016 09:52:25 +0000
- Accept-language: en-GB, en-US
- Cc: Jan Kara <jack@xxxxxxx>, "kernel-hardening@xxxxxxxxxxxxxxxxxx" <kernel-hardening@xxxxxxxxxxxxxxxxxx>, Will Deacon <will.deacon@xxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, "sparclinux@xxxxxxxxxxxxxxx" <sparclinux@xxxxxxxxxxxxxxx>, "linux-ia64@xxxxxxxxxxxxxxx" <linux-ia64@xxxxxxxxxxxxxxx>, Christoph Lameter <cl@xxxxxxxxx>, "Andrea Arcangeli" <aarcange@xxxxxxxxxx>, "linux-arch@xxxxxxxxxxxxxxx" <linux-arch@xxxxxxxxxxxxxxx>, "x86@xxxxxxxxxx" <x86@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, "linux-arm-kernel@xxxxxxxxxxxxxxxxxxx" <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, PaX Team <pageexec@xxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Mathias Krause <minipli@xxxxxxxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, David Rientjes <rientjes@xxxxxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Dmitry Vyukov <dvyukov@xxxxxxxxxx>, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>, Brad Spengler <spender@xxxxxxxxxxxxxx>, "Ard Biesheuvel" <ard.biesheuvel@xxxxxxxxxx>, Pekka Enberg <penberg@xxxxxxxxxx>, Daniel Micay <danielmicay@xxxxxxxxx>, Casey Schaufler <casey@xxxxxxxxxxxxxxxx>, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>, "linuxppc-dev@xxxxxxxxxxxxxxxx" <linuxppc-dev@xxxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>
- In-reply-to: <1468619065-3222-1-git-send-email-keescook@chromium.org>
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- Thread-index: AQHR3uKNcxOYp60hMUWRwOoJRQE2b6AhFJXQ
- Thread-topic: [PATCH v3 00/11] mm: Hardened usercopy
From: Kees Cook
> Sent: 15 July 2016 22:44
> This is a start of the mainline port of PAX_USERCOPY[1].
...
> - if address range is in the current process stack, it must be within the
> current stack frame (if such checking is possible) or at least entirely
> within the current process's stack.
...
That description doesn't seem quite right to me.
I presume the check is:
Within the current process's stack and not crossing the ends of the
current stack frame.
The 'current' stack frame is likely to be that of copy_to/from_user().
Even if you use the stack of the caller, any problematic buffers
are likely to have been passed in from a calling function.
So unless you are going to walk the stack (good luck on that)
I'm not sure checking the stack frames is worth it.
I'd also guess that a lot of copies are from the middle of structures
so cannot fail the tests you are adding.
David
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