linux-kernel - Re: [PATCH 0/5] x86: oops on uaccess faults outside of user addresses

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Date:	Thu, 13 Jun 2013 15:00:37 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, trinity@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 0/5] x86: oops on uaccess faults outside of user addresses

On Wed, May 22, 2013 at 2:07 PM, Andy Lutomirski <luto@...capital.net> wrote:
> Currently, __get_user can't trigger an OOPS -- any exception will be
> caught and return -EFAULT.  This means that, if an access_ok check is
> missing somewhere, then an attacker can freely use it to probe for valid
> kernel mappings.
>
> This series annotates all of the exception fixups as "catch anything" or
> "catch valid uaccess faults", and skips the fixup (and hence oopses) if
> an instruction of the latter type faults for any reason other than a
> page fault to a user address.
>
> I know of only one bug of this type; it's fixed in patch 5.
>
> Perhaps surprisingly, this seems to survive Trinity fairly well.
>
> Andy Lutomirski (5):
>   x86: Split "utter crap" pnpbios fixup out of fixup_exception
>   x86: Clean up extable entry format (and free up a bit)
>   x86: Annotate _ASM_EXTABLE users to distinguish uaccess from
>     everything else
>   x86: Don't fixup uaccess faults to kernel or non-canonical addresses
>   net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg

Patch 5 is (for better or for worse) in -linus now.  What's the status
of the other four?  (They're certainly not 3.10 material.)

--Andy
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