linux-kernel - Re: [PATCH] checkpatch: add warning on %pk instead of %pK usage

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Message-ID: <1486783428.2192.44.camel@perches.com>
Date:   Fri, 10 Feb 2017 19:23:48 -0800
From:   Joe Perches <joe@...ches.com>
To:     "Roberts, William C" <william.c.roberts@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "apw@...onical.com" <apw@...onical.com>
Cc:     "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH] checkpatch: add warning on %pk instead of %pK usage

On Sat, 2017-02-11 at 01:32 +0000, Roberts, William C wrote:
> <snip>
> > > By "normal" I'm referring to things that call into pointer(), just
> > > casually looking I see bstr_printf vsnprintf kvasprintf, which would
> > > be easy enough to add
> > > 
> > > > What do you think is missing?  sn?printf ? That's easy to add.
> > > 
> > > The problem starts to get hairy when we think of how often folks roll
> > > their own logging macros (see some small sampling at the end).
> > > 
> > > I think we would want to add DEBUG DBG and sn?printf and maybe
> > > consider dropping the \b on the regex so it's a bit more matchy but
> > > still shouldn't end up matching on any ASM as you pointed out in the V2 nack.
> > > 
> > > Ill break this down into:
> > > 1. the patch as I know you'll take it, as you wrote it :-P 2. Adding
> > > to the logging macros 3. exploring making it less matchy
> 
> -Kees and Andrew they likely don't care about the rest of this...
> 
> I have been working up a regex (I suck at these) to match C functions that have an invalid
> %p format string and take arguments:
> http://www.regexr.com/3f92k
> 
> This could be a way to get better coverage in a more generic approach, thoughts?

Maybe this: (attached too because Evolution is a bad email client)

It's still kind of hacky, but it does find multiple line
statements like:

+		printf(KERN_INFO
+		       "a %pX",
+		       foo);

---
Subject: [PATCH] checkpatch: Add ability to find bad uses of vsprintf %p extensions

%pK was at least once misused at %pk in an out-of-tree module.
This lead to some security concerns.  Add the ability to track
single and multiple line statements for misuses of %p.

Signed-off-by: Joe Perches 
---
 scripts/checkpatch.pl | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index ad5ea5c545b2..0eaf6b8580d6 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5676,6 +5676,32 @@ sub process {
 			}
 		}
 
+		# check for vsprintf extension %p misuses
+		if ($^V && $^V ge 5.10.0 &&
+		    defined $stat &&
+		    $stat =~ /^\+(?![^\{]*\{\s*).*\b(\w+)\s*\(.*$String\s*,/s &&
+		    $1 !~ /^_*volatile_*$/) {
+			my $bad_extension = "";
+			my $lc = $stat =~ tr@\n@@;
+			$lc = $lc + $linenr;
+		        for (my $count = $linenr; $count <= $lc; $count++) {
+				my $fmt = get_quoted_string($lines[$count - 1], raw_line($count, 0));
+				$fmt =~ s/%%//g;
+				if ($fmt =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGN]).)/) {
+					$bad_extension = $1;
+					last;
+				}
+			}
+			if ($bad_extension ne "") {
+				my $stat_real = raw_line($linenr, 0);
+				for (my $count = $linenr + 1; $count <= $lc; $count++) {
+					$stat_real = $stat_real . "\n" . raw_line($count, 0);
+				}
+				WARN("VSPRINTF_POINTER_EXTENSION",
+				     "Invalid vsprintf pointer extension '$bad_extension'\n" . "$here\n$stat_real\n");
+			}
+		}
+
 # Check for misused memsets
 		if ($^V && $^V ge 5.10.0 &&
 		    defined $stat &&
-- 

View attachment "0001-checkpatch-Add-ability-to-find-bad-uses-of-vsprintf-.patch" of type "text/x-patch" (1886 bytes)