linux-kernel - [PATCH 13/13] Re-enable and clean up "check_config()" in headers

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Date:	Tue,  3 Nov 2015 11:46:34 -0800
From:	Palmer Dabbelt <palmer@...belt.com>
To:	dhowells@...hat.com
Cc:	Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH 13/13] Re-enable and clean up "check_config()" in headers_check.pl

I recently got bit by a CONFIG_ in userspace bug.  This has apparently
happened before, but the check got disabled for triggering too much.
In order to reduce false positives, I added some hueristics to avoid
detecting comments.

Since these tests all pass, I've now re-enabled them.

Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
Reviewed-by: Andrew Waterman <waterman@...s.berkeley.edu>
Reviewed-by: Albert Ou <aou@...s.berkeley.edu>
---
 scripts/headers_check.pl | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/scripts/headers_check.pl b/scripts/headers_check.pl
index 62320f9..1634b51 100755
--- a/scripts/headers_check.pl
+++ b/scripts/headers_check.pl
@@ -27,6 +27,7 @@ my $ret = 0;
 my $line;
 my $lineno = 0;
 my $filename;
+my $check_config_in_multiline_comment = 0;
 
 foreach my $file (@files) {
 	$filename = $file;
@@ -40,7 +41,7 @@ foreach my $file (@files) {
 		&check_asm_types();
 		&check_sizetypes();
 		&check_declarations();
-		# Dropped for now. Too much noise &check_config();
+		&check_config();
 	}
 	close $fh;
 }
@@ -78,7 +79,21 @@ sub check_declarations
 
 sub check_config
 {
-	if ($line =~ m/[^a-zA-Z0-9_]+CONFIG_([a-zA-Z0-9_]+)[^a-zA-Z0-9_]/) {
+	my $nocomments = $line;
+	$nocomments =~ s/\/\*.*\*\///; # Remove ANSI-style comments (/* to */)
+	$nocomments =~ s/\/\/.*//;     # Remove C99-style comments (// to EOL)
+
+	# Check to see if we're within a multiline comment, and if so
+	# just remove the whole line.  I tried matching on '^ * ', but
+	# there's one header that doesn't prepend multi-line comments
+	# with * so that won't work.
+	if ($nocomments =~ m/\/\*/) { $check_config_in_multiline_comment = 1; }
+	if ($nocomments =~ m/\*\//) { $check_config_in_multiline_comment = 0; }
+	if ($check_config_in_multiline_comment == 1) { $nocomments = "" }
+
+	# Check to see if there is something that looks like CONFIG_
+	# inside a userspace-accessible header file and if so, print that out.
+	if ($nocomments =~ m/[^a-zA-Z0-9_]+CONFIG_([a-zA-Z0-9_]+)[^a-zA-Z0-9_]/) {
 		printf STDERR "$filename:$lineno: leaks CONFIG_$1 to userspace where it is not valid\n";
 	}
 }
-- 
2.4.10

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