From: Joao Moreira <joao@overdrivepizza.com>
To: Kees Cook <keescook@chromium.org>
Cc: x86-64-abi@googlegroups.com, kernel-hardening@lists.openwall.com,
samitolvanen@google.com, hjl.tools@gmail.com,
linux-hardening@vger.kernel.org
Subject: Re: Fine-grained Forward CFI on top of Intel CET / IBT
Date: Fri, 19 Mar 2021 15:51:04 -0700 [thread overview]
Message-ID: <632c02ef-efef-c068-1228-1b869d395142@overdrivepizza.com> (raw)
In-Reply-To: <8e7dfa49-2c74-1349-017c-9a4700557519@overdrivepizza.com>
>> That is a good point about R11 availability. Have you examined kernel
>> images for unintended gadgets? It seems like it'd be rare to find an
>> arbitrary R11 load
>> followed by an indirect call together, but stranger gadgets show up, and
>> before the BPF JIT obfuscation happened, it was possible for attackers
>> (with sufficient access) to construct a series of immediates that would
>> contain the needed gadgets. (And not all systems run with BPF JIT
>> hardening enabled.)
>
> I haven't. On a CET-enabled environment, these unintended gadgets
> would need to be preceded with an endbr instruction, otherwise they
> won't be reachable indirectly. I assume that these cases can still
> exist (specially in the presence of things like vulnerable BPF JIT or
> if you consider full non-fineibt-instrumented functions working as
> gadgets), but that this is a raised bar. Besides that, there are
> patches like this one (which unfortunately was abandoned) that could
> come handy:
>
> https://reviews.llvm.org/D88194
>
Actually (as clear in the end of the patch review) this was replaced by
a different patch, which got in :)
review: https://reviews.llvm.org/D89178
commit: https://reviews.llvm.org/rGf385823e04f300c92ec03dbd660d621cc618a271
o/
Joao
prev parent reply other threads:[~2021-03-19 22:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 5:51 Fine-grained Forward CFI on top of Intel CET / IBT Joao Moreira
2021-03-18 20:29 ` Kees Cook
2021-03-19 21:41 ` Joao Moreira
2021-03-19 22:51 ` Joao Moreira [this message]
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