linux-kernel - Re: [PATCH v3 seccomp 1/5] x86: Enable seccomp architecture tracking

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Date:   Wed, 30 Sep 2020 14:21:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     YiFei Zhu <zhuyifei1999@...il.com>
Cc:     containers@...ts.linux-foundation.org,
        YiFei Zhu <yifeifz2@...inois.edu>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, Aleksa Sarai <cyphar@...har.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        David Laight <David.Laight@...lab.com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        Jann Horn <jannh@...gle.com>,
        Josep Torrellas <torrella@...inois.edu>,
        Tianyin Xu <tyxu@...inois.edu>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Tycho Andersen <tycho@...ho.pizza>,
        Valentin Rothberg <vrothber@...hat.com>,
        Will Drewry <wad@...omium.org>
Subject: Re: [PATCH v3 seccomp 1/5] x86: Enable seccomp architecture tracking

On Wed, Sep 30, 2020 at 10:19:12AM -0500, YiFei Zhu wrote:
> From: Kees Cook <keescook@...omium.org>
> 
> Provide seccomp internals with the details to calculate which syscall
> table the running kernel is expecting to deal with. This allows for
> efficient architecture pinning and paves the way for constant-action
> bitmaps.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> [YiFei: Removed x32, added macro for nr_syscalls]
> Signed-off-by: YiFei Zhu <yifeifz2@...inois.edu>
> ---
>  arch/x86/include/asm/seccomp.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h
> index 2bd1338de236..7b3a58271656 100644
> --- a/arch/x86/include/asm/seccomp.h
> +++ b/arch/x86/include/asm/seccomp.h
> @@ -16,6 +16,18 @@
>  #define __NR_seccomp_sigreturn_32	__NR_ia32_sigreturn
>  #endif
>  
> +#ifdef CONFIG_X86_64
> +# define SECCOMP_ARCH_DEFAULT			AUDIT_ARCH_X86_64
> +# define SECCOMP_ARCH_DEFAULT_NR		NR_syscalls

bikeshedding: let's call these SECCOMP_ARCH_NATIVE* -- I think it's more
descriptive.

> +# ifdef CONFIG_COMPAT
> +#  define SECCOMP_ARCH_COMPAT			AUDIT_ARCH_I386
> +#  define SECCOMP_ARCH_COMPAT_NR		IA32_NR_syscalls
> +# endif
> +#else /* !CONFIG_X86_64 */
> +# define SECCOMP_ARCH_DEFAULT		AUDIT_ARCH_I386
> +# define SECCOMP_ARCH_DEFAULT_NR	NR_syscalls
> +#endif
> +
>  #include <asm-generic/seccomp.h>
>  
>  #endif /* _ASM_X86_SECCOMP_H */
> -- 
> 2.28.0
> 

But otherwise, yes, looks good to me. For this patch, I think the S-o-b chain is probably more
accurately captured as:

Signed-off-by: Kees Cook <keescook@...omium.org>
Co-developed-by: YiFei Zhu <yifeifz2@...inois.edu>
Signed-off-by: YiFei Zhu <yifeifz2@...inois.edu>


-- 
Kees Cook