linux-kernel - Re: [PATCH 1/4] module: Expose load

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Message-ID: <202004070951.40A8E7B278@keescook>
Date:   Tue, 7 Apr 2020 09:52:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        hch@...radead.org, sean.j.christopherson@...el.com,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com, x86@...nel.org,
        kenny@...ix.com, jeyu@...nel.org, rasmus.villemoes@...vas.dk,
        pbonzini@...hat.com, fenghua.yu@...el.com, xiaoyao.li@...el.com,
        nadav.amit@...il.com, thellstrom@...are.com, tony.luck@...el.com,
        rostedt@...dmis.org, gregkh@...uxfoundation.org, jannh@...gle.com,
        David.Laight@...lab.com, dcovelli@...are.com, mhiramat@...nel.org
Subject: Re: [PATCH 1/4] module: Expose load_info to arch module loader code

On Tue, Apr 07, 2020 at 01:02:37PM +0200, Peter Zijlstra wrote:
> From: Jessica Yu <jeyu@...nel.org>
> 
> The x86 module loader wants to check the value of a modinfo flag
> (sld_safe), before proceeding to scan the module text for VMX
> instructions. Unfortunately the arch module code currently does not have
> access to load_info, but we can easily expose that via moduleloader.h,
> which every arch module code must already include.
> 
> Signed-off-by: Jessica Yu <jeyu@...nel.org>

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

-Kees

> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Link: https://lkml.kernel.org/r/20200406160420.14407-1-jeyu@kernel.org
> ---
> 
>  include/linux/moduleloader.h | 20 ++++++++++++++++++++
>  kernel/module-internal.h     | 23 -----------------------
>  kernel/module_signing.c      |  2 +-
>  3 files changed, 21 insertions(+), 24 deletions(-)
> 
> Index: linux-2.6/include/linux/moduleloader.h
> ===================================================================
> --- linux-2.6.orig/include/linux/moduleloader.h
> +++ linux-2.6/include/linux/moduleloader.h
> @@ -6,6 +6,26 @@
>  #include <linux/module.h>
>  #include <linux/elf.h>
>  
> +struct load_info {
> +	const char *name;
> +	/* pointer to module in temporary copy, freed at end of load_module() */
> +	struct module *mod;
> +	Elf_Ehdr *hdr;
> +	unsigned long len;
> +	Elf_Shdr *sechdrs;
> +	char *secstrings, *strtab;
> +	unsigned long symoffs, stroffs, init_typeoffs, core_typeoffs;
> +	struct _ddebug *debug;
> +	unsigned int num_debug;
> +	bool sig_ok;
> +#ifdef CONFIG_KALLSYMS
> +	unsigned long mod_kallsyms_init_off;
> +#endif
> +	struct {
> +		unsigned int sym, str, mod, vers, info, pcpu;
> +	} index;
> +};
> +
>  /* These may be implemented by architectures that need to hook into the
>   * module loader code.  Architectures that don't need to do anything special
>   * can just rely on the 'weak' default hooks defined in kernel/module.c.
> Index: linux-2.6/kernel/module-internal.h
> ===================================================================
> --- linux-2.6.orig/kernel/module-internal.h
> +++ linux-2.6/kernel/module-internal.h
> @@ -5,27 +5,4 @@
>   * Written by David Howells (dhowells@...hat.com)
>   */
>  
> -#include <linux/elf.h>
> -#include <asm/module.h>
> -
> -struct load_info {
> -	const char *name;
> -	/* pointer to module in temporary copy, freed at end of load_module() */
> -	struct module *mod;
> -	Elf_Ehdr *hdr;
> -	unsigned long len;
> -	Elf_Shdr *sechdrs;
> -	char *secstrings, *strtab;
> -	unsigned long symoffs, stroffs, init_typeoffs, core_typeoffs;
> -	struct _ddebug *debug;
> -	unsigned int num_debug;
> -	bool sig_ok;
> -#ifdef CONFIG_KALLSYMS
> -	unsigned long mod_kallsyms_init_off;
> -#endif
> -	struct {
> -		unsigned int sym, str, mod, vers, info, pcpu;
> -	} index;
> -};
> -
>  extern int mod_verify_sig(const void *mod, struct load_info *info);
> Index: linux-2.6/kernel/module_signing.c
> ===================================================================
> --- linux-2.6.orig/kernel/module_signing.c
> +++ linux-2.6/kernel/module_signing.c
> @@ -8,11 +8,11 @@
>  #include <linux/kernel.h>
>  #include <linux/errno.h>
>  #include <linux/module.h>
> +#include <linux/moduleloader.h>
>  #include <linux/module_signature.h>
>  #include <linux/string.h>
>  #include <linux/verification.h>
>  #include <crypto/public_key.h>
> -#include "module-internal.h"
>  
>  /*
>   * Verify the signature on a module.
> 
> 

-- 
Kees Cook