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Date: Fri, 10 Feb 2017 19:23:48 -0800
From: Joe Perches <joe@...ches.com>
To: "Roberts, William C" <william.c.roberts@...el.com>,
"linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "apw@...onical.com" <apw@...onical.com>
Cc: "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH] checkpatch: add warning on %pk instead of %pK usage
On Sat, 2017-02-11 at 01:32 +0000, Roberts, William C wrote:
> <snip>
> > > By "normal" I'm referring to things that call into pointer(), just
> > > casually looking I see bstr_printf vsnprintf kvasprintf, which would
> > > be easy enough to add
> > >
> > > > What do you think is missing? sn?printf ? That's easy to add.
> > >
> > > The problem starts to get hairy when we think of how often folks roll
> > > their own logging macros (see some small sampling at the end).
> > >
> > > I think we would want to add DEBUG DBG and sn?printf and maybe
> > > consider dropping the \b on the regex so it's a bit more matchy but
> > > still shouldn't end up matching on any ASM as you pointed out in the V2 nack.
> > >
> > > Ill break this down into:
> > > 1. the patch as I know you'll take it, as you wrote it :-P 2. Adding
> > > to the logging macros 3. exploring making it less matchy
>
> -Kees and Andrew they likely don't care about the rest of this...
>
> I have been working up a regex (I suck at these) to match C functions that have an invalid
> %p format string and take arguments:
> http://www.regexr.com/3f92k
>
> This could be a way to get better coverage in a more generic approach, thoughts?
Maybe this: (attached too because Evolution is a bad email client)
It's still kind of hacky, but it does find multiple line
statements like:
+ printf(KERN_INFO
+ "a %pX",
+ foo);
---
Subject: [PATCH] checkpatch: Add ability to find bad uses of vsprintf %p 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.
Signed-off-by: Joe Perches
---
scripts/checkpatch.pl | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index ad5ea5c545b2..0eaf6b8580d6 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5676,6 +5676,32 @@ sub process {
}
}
+ # check for vsprintf extension %p 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 &&
--
View attachment "0001-checkpatch-Add-ability-to-find-bad-uses-of-vsprintf-.patch" of type "text/x-patch" (1886 bytes)
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