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From: "Tobin C. Harding" <me@tobin.cc>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Tobin C. Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
	Andy Whitcroft <apw@canonical.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v4 4/4] checkpatch: warn for use of %px
Date: Tue, 27 Feb 2018 14:04:08 +1100
Message-ID: <1519700648-23108-5-git-send-email-me@tobin.cc> (raw)
In-Reply-To: <1519700648-23108-1-git-send-email-me@tobin.cc>

Usage of the new %px specifier potentially leaks sensitive
inforamtion. Printing kernel addresses exposes the kernel layout in
memory, this is potentially exploitable. We have tools in the kernel to
help us do the right thing. We can have checkpatch warn developers of
potential dangers of using %px.

Have checkpatch emit a warning for usage of specifier %px.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
Co-Developed-by: Joe Perches <joe@perches.com>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 scripts/checkpatch.pl | 48 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 679a10298cb5..5628e847c6fc 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5797,29 +5797,45 @@ sub process {
 		    defined $stat &&
 		    $stat =~ /^\+(?![^\{]*\{\s*).*\b(\w+)\s*\(.*$String\s*,/s &&
 		    $1 !~ /^_*volatile_*$/) {
-			my $bad_extension = "";
+			my $specifier;
+			my $extension;
+			my $bad_specifier = "";
+			my $stat_real;
+
 			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(?![\WSsBKRraEhMmIiUDdgVCbGNOx]).)/) {
-					$bad_extension = $1;
-					last;
-				}
-			}
-			if ($bad_extension ne "") {
-				my $stat_real = get_stat_real($linenr, $lc);
-				my $ext_type = "Invalid";
-				my $use = "";
-				if ($bad_extension =~ /p[Ff]/) {
-					$ext_type = "Deprecated";
-					$use = " - use %pS instead";
-					$use =~ s/pS/ps/ if ($bad_extension =~ /pf/);
+
+				while ($fmt =~ /(\%[\*\d\.]*p(\w))/g) {
+					$specifier = $1;
+					$extension = $2;
+					if ($extension !~ /[SsBKRraEhMmIiUDdgVCbGNOx]/) {
+						$bad_specifier = $specifier;
+						last;
+					}
+					if ($extension eq "x" && !defined($stat_real)) {
+						if (!defined($stat_real)) {
+							$stat_real = get_stat_real($linenr, $lc);
+						}
+						WARN("VSPRINTF_SPECIFIER_PX",
+						     "Using vsprintf specifier '\%px' potentially exposes the kernel memory layout, if you don't really need the address please consider using '\%p'.\n" . "$here\n$stat_real\n");
+					}
 				}
+				if ($bad_specifier ne "") {
+					my $stat_real = get_stat_real($linenr, $lc);
+					my $ext_type = "Invalid";
+					my $use = "";
+					if ($bad_specifier =~ /p[Ff]/) {
+						$ext_type = "Deprecated";
+						$use = " - use %pS instead";
+						$use =~ s/pS/ps/ if ($bad_specifier =~ /pf/);
+					}
 
-				WARN("VSPRINTF_POINTER_EXTENSION",
-				     "$ext_type vsprintf pointer extension '$bad_extension'$use\n" . "$here\n$stat_real\n");
+					WARN("VSPRINTF_POINTER_EXTENSION",
+					     "$ext_type vsprintf pointer extension '$bad_specifier'$use\n" . "$here\n$stat_real\n");
+				}
 			}
 		}
 
-- 
2.7.4

  parent reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-27  3:04 [PATCH v4 0/4] " Tobin C. Harding
2018-02-27  3:04 ` [PATCH v4 1/4] checkpatch: add sub routine get_stat_real() Tobin C. Harding
2018-02-27  3:04 ` [PATCH v4 2/4] checkpatch: remove unused variable declarations Tobin C. Harding
2018-02-27  3:04 ` [PATCH v4 3/4] checkpatch: add sub routine get_stat_here() Tobin C. Harding
2018-02-27  3:04 ` Tobin C. Harding [this message]
2018-03-02 23:46 ` [PATCH v4 0/4] checkpatch: warn for use of %px Andrew Morton

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