From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, alyssa.milburn@linux.intel.com,
linux-kernel@vger.kernel.org, samitolvanen@google.com,
jpoimboe@kernel.org, joao@overdrivepizza.com,
tim.c.chen@linux.intel.com
Subject: Re: [PATCH 2/2] x86/fineibt: Poison ENDBR at +0
Date: Tue, 20 Jun 2023 14:55:10 -0700 [thread overview]
Message-ID: <202306201454.0A2E875F@keescook> (raw)
In-Reply-To: <20230615193722.194131053@infradead.org>
On Thu, Jun 15, 2023 at 09:35:48PM +0200, Peter Zijlstra wrote:
> Alyssa noticed that when building the kernel with CFI_CLANG+IBT and
> booting on IBT enabled hardware obtain FineIBT, the indirect functions
> look like:
>
> __cfi_foo:
> endbr64
> subl $hash, %r10d
> jz 1f
> ud2
> nop
> 1:
> foo:
> endbr64
>
> This is because clang currently does not supress ENDBR emission for
> functions it provides a __cfi prologue symbol for.
Should this be considered a bug in Clang?
>
> Having this second ENDBR however makes it possible to elide the CFI
> check. Therefore, we should poison this second ENDBR (if present) when
> switching to FineIBT mode.
>
> Fixes: 931ab63664f0 ("x86/ibt: Implement FineIBT")
> Reported-by: "Milburn, Alyssa" <alyssa.milburn@intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Looks like a good work-around.
Acked-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2023-06-20 21:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-15 19:35 [PATCH 0/2] x86/cfi: Fix FineIBT Peter Zijlstra
2023-06-15 19:35 ` [PATCH 1/2] x86/cfi: Fix ret_from_fork indirect calls Peter Zijlstra
2023-06-20 21:56 ` Kees Cook
2023-06-21 8:52 ` Peter Zijlstra
2023-06-21 9:27 ` Peter Zijlstra
2023-06-21 18:08 ` Kees Cook
2023-06-21 18:16 ` Peter Zijlstra
2023-06-21 18:33 ` Peter Zijlstra
2023-06-21 20:13 ` Peter Zijlstra
2023-06-21 21:07 ` Brian Gerst
2023-06-15 19:35 ` [PATCH 2/2] x86/fineibt: Poison ENDBR at +0 Peter Zijlstra
2023-06-20 21:55 ` Kees Cook [this message]
2023-06-21 0:04 ` Sami Tolvanen
2023-06-21 8:51 ` Peter Zijlstra
2023-06-21 8:18 ` Peter Zijlstra
2023-06-21 8:48 ` Peter Zijlstra
2023-06-21 18:07 ` Kees Cook
2023-07-10 8:13 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-06-16 23:24 ` [PATCH 0/2] x86/cfi: Fix FineIBT Sami Tolvanen
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