Author: Peter Senna Tschudin <peter.senna@gmail.com> The semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // @r exists@ position p1,p2; expression x; @@ if (x@p1 == NULL) { … kfree@p2(x); … return …; } @unchanged exists@ position r.p1,r.p2; expression e