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  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]
Date:   Tue, 24 Aug 2021 10:26:16 -0700
From:   Tom Stellard <>
To:     Sami Tolvanen <>
Cc:     X86 ML <>, Kees Cook <>,
        Josh Poimboeuf <>,
        Peter Zijlstra <>,
        Nathan Chancellor <>,
        Nick Desaulniers <>,
        Sedat Dilek <>,,
        LKML <>,
        clang-built-linux <>
Subject: Re: [PATCH v2 00/14] x86: Add support for Clang CFI

On 8/23/21 10:20 AM, Sami Tolvanen wrote:
> On Mon, Aug 23, 2021 at 10:16 AM Tom Stellard <> wrote:
>> On 8/23/21 10:13 AM, 'Sami Tolvanen' via Clang Built Linux wrote:
>>> This series adds support for Clang's Control-Flow Integrity (CFI)
>>> checking to x86_64. With CFI, the compiler injects a runtime
>>> check before each indirect function call to ensure the target is
>>> a valid function with the correct static type. This restricts
>>> possible call targets and makes it more difficult for an attacker
>>> to exploit bugs that allow the modification of stored function
>>> pointers. For more details, see:
>>> Version 2 depends on Clang >=14, where we fixed the issue with
>>> referencing static functions from inline assembly. Based on the
>>> feedback for v1, this version also changes the declaration of
>>> functions that are not callable from C to use an opaque type,
>>> which stops the compiler from replacing references to them. This
>>> avoids the need to sprinkle function_nocfi() macros in the kernel
>>> code.
>> How invasive are the changes in clang 14 necessary to make CFI work?
>> Would it be possible to backport them to LLVM 13?
> I'm not sure what the LLVM backport policy is, but this specific fix
> was quite simple:

That looks like something we could backport, I filed a bug to track
the backport:

Do you have any concerns about backporting it or do you think it's pretty


> Sami

Powered by blists - more mailing lists