[PATCH v2] coccinelle: free: add a checker for `__cleanup(kfree)` usage

[Ella Ma <alansnape3058@gmail.com>]

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@gmail.com>
---

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`

Currently, the five functions in the `free` rule are all the functions
of `void (*)(const? void *)` type with a `DEFINE_FREE` definition in the
code base. So I adopted all of them.
Function `kfree_const` is added as it is of the kfree family and used
more frequently than other kfree-family functions (even more frequently
than some of those having a `DEFINE_FREE` definition).
https://elixir.bootlin.com/linux/v7.3-rc3/A/ident/kfree_const
(found in 64 files in v7.3-rc3).

This cocci script can report the bug fixed in
https://lore.kernel.org/lkml/20260617142632.3298984-1-vulab@iscas.ac.cn/

 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..63216ec5d865
--- /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;
+@@
+
+coccilib.report.print_report(
+  p[0], f"ERROR: found `__cleanup({n})', do you mean `__free({n})'?")
+
+@script:python depends on org@
+p << free.p;
+n << free.n;
+@@
+
+coccilib.org.print_todo(
+  p[0], f"ERROR: found `__cleanup({n})', do you mean `__free({n})'?")
+
+
+// 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;
+@@
+
+coccilib.report.print_report(
+  p[0], f"ERROR: `__cleanup({n})' will free the annotated variable, rather than its pointee")
+
+@script:python depends on org@
+p << cleanup.p;
+n << cleanup.n;
+@@
+
+coccilib.org.print_todo(
+  p[0], f"ERROR: `__cleanup({n})' will free the annotated variable, rather than its pointee")
-- 
2.34.1