[PATCH v3] coccinelle: free: add a checker for `__cleanup(kfree)` usage

[Ella Ma]

Using __cleanup(kfree) will pass the stack address of the annotated
local variable to kfree functions. This will lead to invalid
deallocation issues. Inspired by CVE-2026-45959 and similar bugs
recently detected.

Signed-off-by: Ella Ma <alansnape3058@xxxxxxxxx>
---

Changes in v2:
- Add virtual rules `report` and `org` as suggested by Sashiko
- Remove `kvfree_sensitive` from rule `cleanup` as suggested by Sashiko
- Add `free_percpu` to rule `free`
- Add `kfree_const` to rule `cleanup`

Changes in v3:
- Edit the error messages to clarify the reasons and results

 scripts/coccinelle/free/cleanup-free.cocci | 112 +++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 scripts/coccinelle/free/cleanup-free.cocci

diff --git a/scripts/coccinelle/free/cleanup-free.cocci b/scripts/coccinelle/free/cleanup-free.cocci
new file mode 100644
index 000000000000..48e47ed2186a
--- /dev/null
+++ b/scripts/coccinelle/free/cleanup-free.cocci
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Find __cleanup(kfree)
+/// Using __cleanup(kfree) will pass the stack address of the annotated
+/// local variable to kfree, causing an invalid free.
+/// I.e., `T v __cleanup(kfree);` --> `kfree(&v);`
+/// Such usage is impossible to be correct.
+///
+// Confidence: High
+// Copyright: (C) 2026 Ella Ma
+// Options: --no-includes --include-headers
+
+virtual report
+virtual org
+
+// Suggesting using __free for the functions with a DEFINE_FREE definition.
+// Update this list when new DEFINE_FREE definitions are added.
+@free@
+attribute name __cleanup;
+symbol kfree, kfree_sensitive, kvfree, kvfree_atomic, free_percpu;
+type T;
+identifier v, n;
+position p;
+@@
+
+(
+  T v __cleanup@p(
+(
+  n
+&
+(
+  kfree \| kfree_sensitive \| kvfree \| kvfree_atomic \| free_percpu
+)
+)
+  );
+|
+  T v __cleanup@p(
+(
+  n
+&
+(
+  kfree \| kfree_sensitive \| kvfree \| kvfree_atomic \| free_percpu
+)
+)
+  ) = ...;
+)
+
+@script:python depends on report@
+p << free.p;
+n << free.n;
+@@
+
+msg = f"ERROR: __cleanup({n}) will cause an invalid free: the stack address of the annotated variable will be passed to {n}; use __free({n}) to free the pointee"
+coccilib.report.print_report(p[0], msg)
+
+@script:python depends on org@
+p << free.p;
+n << free.n;
+@@
+
+msg = f"ERROR: __cleanup({n}) will cause an invalid free: the stack address of the annotated variable will be passed to {n}; use __free({n}) to free the pointee"
+coccilib.org.print_todo(p[0], msg)
+
+
+// Reporting __cleanup usage for the functions without a DEFINE_FREE definition.
+// The following list only contains frequently used functions. Supplement it if
+// necessary.
+@cleanup@
+attribute name __cleanup;
+symbol vfree, vfree_atomic, kfree_const;
+type T;
+identifier v, n;
+position p;
+@@
+
+(
+  T v __cleanup@p(
+(
+  n
+&
+(
+  vfree \| vfree_atomic \| kfree_const
+)
+)
+  );
+|
+  T v __cleanup@p(
+(
+  n
+&
+(
+  vfree \| vfree_atomic \| kfree_const
+)
+)
+  ) = ...;
+)
+
+@script:python depends on report@
+p << cleanup.p;
+n << cleanup.n;
+@@
+
+msg = f"ERROR: __cleanup({n}) will cause an invalid free: the stack address of the annotated variable will be passed to {n}"
+coccilib.report.print_report(p[0], msg)
+
+@script:python depends on org@
+p << cleanup.p;
+n << cleanup.n;
+@@
+
+msg = f"ERROR: __cleanup({n}) will cause an invalid free: the stack address of the annotated variable will be passed to {n}"
+coccilib.org.print_todo(p[0], msg)
-- 
2.34.1