From e3c6bc95668b9b9fc1e74f221551dfa622ea9061 Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Tue, 10 Apr 2018 16:33:31 -0700
Subject: [PATCH] checkpatch: warn for use of %px

Usage of the new %px specifier potentially leaks sensitive information.
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.

Link: http://lkml.kernel.org/r/1519700648-23108-5-git-send-email-me@tobin.cc
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 scripts/checkpatch.pl | 50 ++++++++++++++++++++++++++++---------------
 1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8be5297d18b6..788c90c1ae2a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5812,29 +5812,45 @@ 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/);
-				}
 
-				WARN("VSPRINTF_POINTER_EXTENSION",
-				     "$ext_type vsprintf pointer extension '$bad_extension'$use\n" . "$here\n$stat_real\n");
+				while ($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_specifier'$use\n" . "$here\n$stat_real\n");
+				}
 			}
 		}