linux-kernel - Re: [PATCH] checkpatch: match more world writable permissions

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Date:	Sat, 14 Mar 2015 08:42:09 -0700
From:	Joe Perches <joe@...ches.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Whitcroft <apw@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] checkpatch: match more world writable permissions

On Sat, 2015-03-14 at 07:32 -0700, Guenter Roeck wrote:
> On Fri, Mar 13, 2015 at 04:43:43PM -0700, Joe Perches wrote:
> > Currently checkpatch will fuss if one uses world writable
> > settings in debugfs files and DEVICE_ATTR uses by testing
> > S_IWUGO but not testing S_IWOTH, S_IRWXUGO or S_IALLUGO.
> > 
> > Extend the check to catch all cases exporting world writable
> > permissions including octal values.
> > 
> > Original-patch-by: Nicholas Mc Guire <hofrat@...dl.org>
> > Signed-off-by: Joe Perches <joe@...ches.com>
> > ---
> >  scripts/checkpatch.pl | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index 6b79beb..4f07d50 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -443,6 +443,14 @@ foreach my $entry (@mode_permission_funcs) {
> >  	$mode_perms_search .= $entry->[0];
> >  }
> >  
> > +$our $mode_perms_world_writable = qr{
> > +	S_IWUGO		|
> > +	S_IWOTH		|
> > +	S_IRWXUGO	|
> > +	S_IALLUGO	|
> > +	0[0-7][0-7][2367]
> > +}x;
> > +
> >  our $allowed_asm_includes = qr{(?x:
> >  	irq|
> >  	memory|
> > @@ -5356,8 +5364,8 @@ sub process {
> >  			}
> >  		}
> >  
> > -		if ($line =~ /debugfs_create_file.*S_IWUGO/ ||
> > -		    $line =~ /DEVICE_ATTR.*S_IWUGO/ ) {
> > +		if ($line =~ /debugfs_create_\w+.*\b$mode_perms_world_writable\b/ ||
> > +		    $line =~ /DEVICE_ATTR.*\b$mode_perms_world_writable\b/) {
> >  			WARN("EXPORTED_WORLD_WRITABLE",
> >  			     "Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
> 
> With https://lkml.org/lkml/2015/3/12/412 in mind, maybe this should be
> marked as error, at least for sysfs attributes.

Maybe it's time for the debate this commit referenced:

commit 58f86cc89c3372d3e61d5b71e5513ec5a0b02848
Author: Rusty Russell <rusty@...tcorp.com.au>
Date:   Mon Mar 24 12:00:34 2014 +1030

    VERIFY_OCTAL_PERMISSIONS: stricter checking for sysfs perms.
    
    Summary of http://lkml.org/lkml/2014/3/14/363 :
    
      Ted: module_param(queue_depth, int, 444)
      Joe: 0444!
      Rusty: User perms >= group perms >= other perms?
      Joe: CLASS_ATTR, DEVICE_ATTR, SENSOR_ATTR and SENSOR_ATTR_2?
    
    Side effect of stricter permissions means removing the unnecessary
    S_IFREG from several callers.
    
    Note that the BUILD_BUG_ON_ZERO((perm) & 2) test was removed: a fair
    number of drivers fail this test, so that will be the debate for a
    future patch.
    


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