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>.

[akpm@linux-foundation.org: add helpful comment into lib/vsprintf.c]
[akpm@linux-foundation.org: text tweak]
Link: http://lkml.kernel.org/r/163a690510e636a23187c0dc9caa09ddac6d4cde.1488228427.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: William Roberts <william.c.roberts@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 30eeba4f1602..732bb3e2fe9a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5663,6 +5663,32 @@ 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 &&