linux-kernel - Re: [PATCH 1/7] modpost: add strict white-listing when referencing sections.

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Date:	Fri, 20 Mar 2015 11:59:41 +1030
From:	Rusty Russell <rusty@...abs.org>
To:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH 1/7] modpost: add strict white-listing when referencing sections.

Quentin Casasnovas <quentin.casasnovas@...cle.com> writes:
> Prints a warning when a section references a section outside a strict
> white-list.  This will be useful to print a warning if __ex_table
> references a non-executable section.

Hi Quentin,

        Really pleasant to read these patches; nice work!

> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index d439856..7094a57 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -925,7 +925,8 @@ enum mismatch {
>  
>  struct sectioncheck {
>  	const char *fromsec[20];
> -	const char *tosec[20];
> +	const char *bad_tosec[20];
> +	const char *good_tosec[20];
>  	enum mismatch mismatch;
>  	const char *symbol_white_list[20];

My only gripe is that these fields are undocumented.  You maintain
the status quo, but some comments indicating what the mean would be
nice.  Perhaps as a separate patch.

In case you need it (for the whole series):
        Acked-by: Rusty Russell <rusty@...tcorp.com.au>

Thanks,
Rusty.

>  };
> @@ -936,19 +937,19 @@ static const struct sectioncheck sectioncheck[] = {
>   */
>  {
>  	.fromsec = { TEXT_SECTIONS, NULL },
> -	.tosec   = { ALL_INIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_INIT_SECTIONS, NULL },
>  	.mismatch = TEXT_TO_ANY_INIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  {
>  	.fromsec = { DATA_SECTIONS, NULL },
> -	.tosec   = { ALL_XXXINIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_XXXINIT_SECTIONS, NULL },
>  	.mismatch = DATA_TO_ANY_INIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  {
>  	.fromsec = { DATA_SECTIONS, NULL },
> -	.tosec   = { INIT_SECTIONS, NULL },
> +	.bad_tosec = { INIT_SECTIONS, NULL },
>  	.mismatch = DATA_TO_ANY_INIT,
>  	.symbol_white_list = {
>  		"*_template", "*_timer", "*_sht", "*_ops",
> @@ -957,54 +958,54 @@ static const struct sectioncheck sectioncheck[] = {
>  },
>  {
>  	.fromsec = { TEXT_SECTIONS, NULL },
> -	.tosec   = { ALL_EXIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
>  	.mismatch = TEXT_TO_ANY_EXIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  {
>  	.fromsec = { DATA_SECTIONS, NULL },
> -	.tosec   = { ALL_EXIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
>  	.mismatch = DATA_TO_ANY_EXIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  /* Do not reference init code/data from meminit code/data */
>  {
>  	.fromsec = { ALL_XXXINIT_SECTIONS, NULL },
> -	.tosec   = { INIT_SECTIONS, NULL },
> +	.bad_tosec = { INIT_SECTIONS, NULL },
>  	.mismatch = XXXINIT_TO_SOME_INIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  /* Do not reference exit code/data from memexit code/data */
>  {
>  	.fromsec = { ALL_XXXEXIT_SECTIONS, NULL },
> -	.tosec   = { EXIT_SECTIONS, NULL },
> +	.bad_tosec = { EXIT_SECTIONS, NULL },
>  	.mismatch = XXXEXIT_TO_SOME_EXIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  /* Do not use exit code/data from init code */
>  {
>  	.fromsec = { ALL_INIT_SECTIONS, NULL },
> -	.tosec   = { ALL_EXIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
>  	.mismatch = ANY_INIT_TO_ANY_EXIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  /* Do not use init code/data from exit code */
>  {
>  	.fromsec = { ALL_EXIT_SECTIONS, NULL },
> -	.tosec   = { ALL_INIT_SECTIONS, NULL },
> +	.bad_tosec = { ALL_INIT_SECTIONS, NULL },
>  	.mismatch = ANY_EXIT_TO_ANY_INIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  },
>  {
>  	.fromsec = { ALL_PCI_INIT_SECTIONS, NULL },
> -	.tosec   = { INIT_SECTIONS, NULL },
> +	.bad_tosec = { INIT_SECTIONS, NULL },
>  	.mismatch = ANY_INIT_TO_ANY_EXIT,
>  	.symbol_white_list = { NULL },
>  },
>  /* Do not export init/exit functions or data */
>  {
>  	.fromsec = { "__ksymtab*", NULL },
> -	.tosec   = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
> +	.bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
>  	.mismatch = EXPORT_TO_INIT_EXIT,
>  	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
>  }
> @@ -1018,9 +1019,12 @@ static const struct sectioncheck *section_mismatch(
>  	const struct sectioncheck *check = &sectioncheck[0];
>  
>  	for (i = 0; i < elems; i++) {
> -		if (match(fromsec, check->fromsec) &&
> -		    match(tosec, check->tosec))
> -			return check;
> +		if (match(fromsec, check->fromsec)) {
> +			if (check->bad_tosec[0] && match(tosec, check->bad_tosec))
> +				return check;
> +			if (check->good_tosec[0] && !match(tosec, check->good_tosec))
> +				return check;
> +		}
>  		check++;
>  	}
>  	return NULL;
> -- 
> 2.0.5
>
> --
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