linux-kernel - [PATCH V2] scripts/coccinelle/free: add NULL test before freeing functions

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Message-Id: <1403899335-3867-1-git-send-email-fabf@skynet.be>
Date:	Fri, 27 Jun 2014 22:02:15 +0200
From:	Fabian Frederick <fabf@...net.be>
To:	linux-kernel@...r.kernel.org
Cc:	Fabian Frederick <fabf@...net.be>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Joe Perches <joe@...ches.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH V2] scripts/coccinelle/free: add NULL test before freeing functions

Warns on NULL check before the following functions:

kfree
usb_free_urb
debugfs_remove
debugfs_remove_recursive

Cc: Julia Lawall <Julia.Lawall@...6.fr>
Cc: Gilles Muller <Gilles.Muller@...6.fr>
Cc: Joe Perches <joe@...ches.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@...net.be>
---
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 | 34 ++++++++++++++++++++++++++++++++
 1 file changed, 34 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..626309c
--- /dev/null
+++ b/scripts/coccinelle/free/ifnullfree.cocci
@@ -0,0 +1,34 @@
+/// 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 org
+virtual report
+virtual context
+
+@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);
+
+@...ipt:python depends on org@
+p << r.p;
+@@
+
+cocci.print_main("freeing", p)
+
+@...ipt: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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