[PATCH V3] scripts/coccinelle/free: add NULL test before freeing functions

[Fabian Frederick]

Warns or generates patch for NULL check before the following functions:

kfree
usb_free_urb
debugfs_remove
debugfs_remove_recursive

Cc: Julia Lawall <Julia.Lawall@xxxxxxx>
Cc: Gilles Muller <Gilles.Muller@xxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
---

V3: 
   -Update print_main message.
   -Add patch mode (suggested by Julia Lawall)

V2:
   -Add 3 more functions to kfree (suggested by Joe Perches)
   -Update warning message to involve code analysis (suggested by Julia Lawall)

 scripts/coccinelle/free/ifnullfree.cocci | 53 ++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 scripts/coccinelle/free/ifnullfree.cocci

diff --git a/scripts/coccinelle/free/ifnullfree.cocci b/scripts/coccinelle/free/ifnullfree.cocci
new file mode 100644
index 0000000..c826d98
--- /dev/null
+++ b/scripts/coccinelle/free/ifnullfree.cocci
@@ -0,0 +1,53 @@
+/// NULL check before some freeing functions is not needed.
+///
+/// Based on checkpatch warning
+/// "kfree(NULL) is safe this check is probably not required"
+/// and kfreeaddr.cocci by Julia Lawall.
+///
+/// Comments: -
+/// Options: --no-includes --include-headers
+
+virtual patch
+virtual org
+virtual report
+virtual context
+
+@r2 depends on patch@
+expression E;
+@@
+- if (E)
+(
+-	kfree(E);
++ kfree(E);
+|
+-	debugfs_remove(E);
++ debugfs_remove(E);
+|
+-	debugfs_remove_recursive(E);
++ debugfs_remove_recursive(E);
+|
+-	usb_free_urb(E);
++ usb_free_urb(E);
+)
+
+@r depends on context || report || org @
+expression E;
+position p;
+@@
+
+* if (E)
+*	\(kfree@p\|debugfs_remove@p\|debugfs_remove_recursive@p\|usb_free_urb\)(E);
+
+@script:python depends on org@
+p << r.p;
+@@
+
+cocci.print_main("NULL check before that freeing function is not needed", p)
+
+@script:python depends on report@
+p << r.p;
+@@
+
+msg = "WARNING: NULL check before freeing functions like kfree, debugfs_remove, debugfs_remove_recursive or usb_free_urb is not needed. Maybe consider reorganizing relevant code to avoid passing NULL values."
+coccilib.report.print_report(p[0], msg)
+
-- 
1.8.4.5

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