linux-kernel - [PATCH] checkpatch: Add ability to find bad uses of vsprintf %p<foo> extensions

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Message-Id: <163a690510e636a23187c0dc9caa09ddac6d4cde.1488228427.git.joe@perches.com>
Date:   Mon, 27 Feb 2017 12:54:55 -0800
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Whitcroft <apw@...onical.com>
Cc:     "Roberts, William C" <william.c.roberts@...el.com>,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org
Subject: [PATCH] checkpatch: Add ability to find bad uses of vsprintf %p<foo> 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<foo>.

Signed-off-by: Joe Perches <joe@...ches.com>
---

Andrew, this has gone back and forth a few times.

It's imperfect as a patch context with just a single
function addition can be missed, but that's not new
with $stat tests and just this patch.  Perhaps one day
the $stat identification mechanism can be improved.

Until then, can you please apply this?  Thanks.

 scripts/checkpatch.pl | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index ad5ea5c545b2..9293b8a1c121 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5676,6 +5676,32 @@ sub process {
 			}
 		}
 
+		# check for vsprintf extension %p<foo> 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 &&
-- 
2.10.0.rc2.1.g053435c