lists.openwall.net   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  linux-cve-announce  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]
Message-ID: <202301121452.37FE29F29B@keescook>
Date:   Thu, 12 Jan 2023 14:52:04 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] kbuild: Fix CFI hash randomization with KASAN

On Thu, Jan 12, 2023 at 10:49:48PM +0000, Sami Tolvanen wrote:
> Clang emits a asan.module_ctor constructor to each object file
> when KASAN is enabled, and these functions are indirectly called
> in do_ctors. With CONFIG_CFI_CLANG, the compiler also emits a CFI
> type hash before each address-taken global function so they can
> pass indirect call checks.
> 
> However, in commit 0c3e806ec0f9 ("x86/cfi: Add boot time hash
> randomization"), x86 implemented boot time hash randomization,
> which relies on the .cfi_sites section generated by objtool. As
> objtool is run against vmlinux.o instead of individual object
> files with X86_KERNEL_IBT (enabled by default), CFI types in
> object files that are not part of vmlinux.o end up not being
> included in .cfi_sites, and thus won't get randomized and trip
> CFI when called.
> 
> Only .vmlinux.export.o and init/version-timestamp.o are linked
> into vmlinux separately from vmlinux.o. As these files don't
> contain any functions, disable KASAN for both of them to avoid
> breaking hash randomization.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1742
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ