linux-kernel - [PATCH v4] coccinelle: api: add kzfree script

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Date:   Fri, 17 Jul 2020 14:57:09 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Denis Efremov <efremov@...ux.com>, cocci@...teme.lip6.fr,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4] coccinelle: api: add kzfree script

Check for memset()/memzero_explicit() followed by kfree()/vfree()/kvfree().

Signed-off-by: Denis Efremov <efremov@...ux.com>
---
Changes in v2:
 - memset_explicit() added
 - kvfree_sensitive() added
 - forall added to r1
 - ... between memset and kfree added
Changes in v3:
 - Explicit filter for definitions instead of !(file in "...") conditions
 - type T added to match casts
 - memzero_explicit() patterns fixed
 - additional rule "cond" added to filter false-positives
Changes in v4:
 - memset call fixed in rp_memset
 - @m added to rp_memset,rp_memzero rules

 scripts/coccinelle/api/kzfree.cocci | 101 ++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 scripts/coccinelle/api/kzfree.cocci

diff --git a/scripts/coccinelle/api/kzfree.cocci b/scripts/coccinelle/api/kzfree.cocci
new file mode 100644
index 000000000000..33625bd7cec9
--- /dev/null
+++ b/scripts/coccinelle/api/kzfree.cocci
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Use kzfree, kvfree_sensitive rather than memset or
+/// memzero_explicit followed by kfree
+///
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS
+// Options: --no-includes --include-headers
+//
+// Keywords: kzfree, kvfree_sensitive
+//
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+@...tialize:python@
+@@
+# kmalloc_oob_in_memset uses memset to explicitly trigger out-of-bounds access
+filter = frozenset(['kmalloc_oob_in_memset', 'kzfree', 'kvfree_sensitive'])
+
+def relevant(p):
+    return not (filter & {el.current_element for el in p})
+
+@...d@
+position ok;
+@@
+
+if (...)
+  \(memset@ok\|memzero_explicit@ok\)(...);
+
+@r depends on !patch forall@
+expression E;
+position p : script:python() { relevant(p) };
+position m != cond.ok;
+type T;
+@@
+
+(
+* memset@m((T)E, 0, ...);
+|
+* memzero_explicit@m((T)E, ...);
+)
+  ... when != E
+      when strict
+* \(kfree\|vfree\|kvfree\)(E)@p;
+
+@...memzero depends on patch@
+expression E, size;
+position p : script:python() { relevant(p) };
+position m != cond.ok;
+type T;
+@@
+
+- memzero_explicit@m((T)E, size);
+  ... when != E
+      when strict
+// TODO: uncomment when kfree_sensitive will be merged.
+// Only this case is commented out because developers
+// may not like patches like this since kzfree uses memset
+// internally (not memzero_explicit).
+//(
+//- kfree(E)@p;
+//+ kfree_sensitive(E);
+//|
+- \(vfree\|kvfree\)(E)@p;
++ kvfree_sensitive(E, size);
+//)
+
+@...memset depends on patch@
+expression E, size;
+position p : script:python() { relevant(p) };
+position m != cond.ok;
+type T;
+@@
+
+- memset@m((T)E, 0, size);
+  ... when != E
+      when strict
+(
+- kfree(E)@p;
++ kzfree(E);
+|
+- \(vfree\|kvfree\)(E)@p;
++ kvfree_sensitive(E, size);
+)
+
+@...ipt:python depends on report@
+p << r.p;
+@@
+
+coccilib.report.print_report(p[0],
+  "WARNING: opportunity for kzfree/kvfree_sensitive")
+
+@...ipt:python depends on org@
+p << r.p;
+@@
+
+coccilib.org.print_todo(p[0],
+  "WARNING: opportunity for kzfree/kvfree_sensitive")
-- 
2.26.2