linux-kernel - [PATCH v2] checkpatch: add warning on invalid %p extensions

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Message-Id: <1486766608-8791-1-git-send-email-william.c.roberts@intel.com>
Date:   Fri, 10 Feb 2017 14:43:28 -0800
From:   william.c.roberts@...el.com
To:     linux-kernel@...r.kernel.org, joe@...ches.com, apw@...onical.com
Cc:     keescook@...omium.org, kernel-hardening@...ts.openwall.com,
        William Roberts <william.c.roberts@...el.com>
Subject: [PATCH v2] checkpatch: add warning on invalid %p extensions

From: William Roberts <william.c.roberts@...el.com>

The kernel supports %p extensions as documented in
Documentation/printk-formats.txt. Warn on possibly
improper use of non-extension characters.

One issue would be the usage of %pk when %pK should have
been used. This has a side-effect of appearing to work
alright, but does not respect the kptr_restrict setting
as %pK does.

Sample output:
WARNING: Invalid vsprintf pointer extension '%pk'
+			printk(KERN_INFO "Could not allocate IRQ %d for PCI Applicom device. %pk\n", dev->irq, pci_get_class); // NOT OK

WARNING: Invalid vsprintf pointer extension '%pn'
+			sprintf(buf, "%pn", x); // NOT OK

Signed-off-by: William Roberts <william.c.roberts@...el.com>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 982c52c..fa22751 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6096,6 +6096,12 @@ sub process {
 			      "recursive locking is bad, do not use this ever.\n" . $herecurr);
 		}
 
+# check for vsprintf extension %p<foo> misuses
+		if (get_quoted_string($line, $rawline) =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGN]).)/) {
+			WARN("VSPRINTF_POINTER_EXTENSION",
+			     "Invalid vsprintf pointer extension '$1'\n" . $herecurr);
+		}
+
 # check for lockdep_set_novalidate_class
 		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
 		    $line =~ /__lockdep_no_validate__\s*\)/ ) {
-- 
2.7.4