coccinelle: iterators: Add for_each_child.cocci script

While iterating over child nodes with the for_each functions, if
control is transferred from the middle of the loop, as in the case
of a break or return or goto, there is no decrement in the
reference counter thus ultimately resulting in a memory leak.

Add this script to detect potential memory leaks caused by
the absence of of_node_put() before break, goto, or, return
statements which transfer control outside the loop.
Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>

scripts/coccinelle/iterators/for_each_child.cocci

+// SPDX-License-Identifier: GPL-2.0-only
+// Adds missing of_node_put() before return/break/goto statement within a for_each iterator for child nodes.
+//# False positives can be due to function calls within the for_each
+//# loop that may encapsulate an of_node_put.
+///
+// Confidence: High
+// Copyright: (C) 2020 Sumera Priyadarsini
+// URL: http://coccinelle.lip6.fr
+// Options: --no-includes --include-headers
+
+virtual patch
+virtual context
+virtual org
+virtual report
+
+@r@
+local idexpression n;
+expression e1,e2;
+iterator name for_each_node_by_name, for_each_node_by_type,
+for_each_compatible_node, for_each_matching_node,
+for_each_matching_node_and_match, for_each_child_of_node,
+for_each_available_child_of_node, for_each_node_with_property;
+iterator i;
+statement S;
+expression list [n1] es;
+@@
+
+(
+(
+for_each_node_by_name(n,e1) S
+|
+for_each_node_by_type(n,e1) S
+|
+for_each_compatible_node(n,e1,e2) S
+|
+for_each_matching_node(n,e1) S
+|
+for_each_matching_node_and_match(n,e1,e2) S
+|
+for_each_child_of_node(e1,n) S
+|
+for_each_available_child_of_node(e1,n) S
+|
+for_each_node_with_property(n,e1) S
+)
+&
+i(es,n,...) S
+)
+
+@ruleone depends on patch && !context && !org && !report@
+
+local idexpression r.n;
+iterator r.i,i1;
+expression e;
+expression list [r.n1] es;
+statement S;
+@@
+
+ i(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   return n;
+|
+   i1(...,n,...) S
+|
+- return of_node_get(n);
++ return n;
+|
++  of_node_put(n);
+?  return ...;
+)
+   ... when any
+ }
+
+@ruletwo depends on patch && !context && !org && !report@
+
+local idexpression r.n;
+iterator r.i,i1,i2;
+expression e,e1;
+expression list [r.n1] es;
+statement S,S2;
+@@
+
+ i(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   i1(...,n,...) S
+|
++  of_node_put(n);
+?  break;
+)
+   ... when any
+ }
+... when != n
+    when strict
+    when forall
+(
+ n = e1;
+|
+?i2(...,n,...) S2
+)
+
+@rulethree depends on patch && !context && !org && !report exists@
+
+local idexpression r.n;
+iterator r.i,i1,i2;
+expression e,e1;
+identifier l;
+expression list [r.n1] es;
+statement S,S2;
+@@
+
+ i(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   i1(...,n,...) S
+|
++  of_node_put(n);
+?  goto l;
+)
+   ... when any
+ }
+... when exists
+l: ... when != n
+       when strict
+       when forall
+(
+ n = e1;
+|
+?i2(...,n,...) S2
+)
+
+// ----------------------------------------------------------------------------
+
+@ruleone_context depends on !patch && (context || org || report) exists@
+statement S;
+expression e;
+expression list[r.n1] es;
+iterator r.i, i1;
+local idexpression r.n;
+position j0, j1;
+@@
+
+ i@j0(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   return n;
+|
+   i1(...,n,...) S
+|
+  return @j1 ...;
+)
+   ... when any
+ }
+
+@ruleone_disj depends on !patch && (context || org || report)@
+expression list[r.n1] es;
+iterator r.i;
+local idexpression r.n;
+position ruleone_context.j0, ruleone_context.j1;
+@@
+
+*  i@j0(es,n,...) {
+   ...
+*return  @j1...;
+   ... when any
+ }
+
+@ruletwo_context depends on !patch && (context || org || report) exists@
+statement S, S2;
+expression e, e1;
+expression list[r.n1] es;
+iterator r.i, i1, i2;
+local idexpression r.n;
+position j0, j2;
+@@
+
+ i@j0(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   i1(...,n,...) S
+|
+  break@j2;
+)
+   ... when any
+ }
+... when != n
+    when strict
+    when forall
+(
+ n = e1;
+|
+?i2(...,n,...) S2
+)
+
+@ruletwo_disj depends on !patch && (context || org || report)@
+statement S2;
+expression e1;
+expression list[r.n1] es;
+iterator r.i, i2;
+local idexpression r.n;
+position ruletwo_context.j0, ruletwo_context.j2;
+@@
+
+*  i@j0(es,n,...) {
+   ...
+*break @j2;
+   ... when any
+ }
+... when != n
+    when strict
+    when forall
+(
+  n = e1;
+|
+?i2(...,n,...) S2
+)
+
+@rulethree_context depends on !patch && (context || org || report) exists@
+identifier l;
+statement S,S2;
+expression e, e1;
+expression list[r.n1] es;
+iterator r.i, i1, i2;
+local idexpression r.n;
+position j0, j3;
+@@
+
+ i@j0(es,n,...) {
+   ...
+(
+   of_node_put(n);
+|
+   e = n
+|
+   i1(...,n,...) S
+|
+  goto l@j3;
+)
+  ... when any
+ }
+... when exists
+l:
+... when != n
+    when strict
+    when forall
+(
+ n = e1;
+|
+?i2(...,n,...) S2
+)
+
+@rulethree_disj depends on !patch && (context || org || report) exists@
+identifier l;
+statement S2;
+expression e1;
+expression list[r.n1] es;
+iterator r.i, i2;
+local idexpression r.n;
+position rulethree_context.j0, rulethree_context.j3;
+@@
+
+*  i@j0(es,n,...) {
+   ...
+*goto l@j3;
+   ... when any
+ }
+... when exists
+ l:
+ ... when != n
+     when strict
+     when forall
+(
+ n = e1;
+|
+?i2(...,n,...) S2
+)
+
+// ----------------------------------------------------------------------------
+
+@script:python ruleone_org depends on org@
+i << r.i;
+j0 << ruleone_context.j0;
+j1 << ruleone_context. j1;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before return " % (i)
+coccilib.org.print_safe_todo(j0[0], msg)
+coccilib.org.print_link(j1[0], "")
+
+@script:python ruletwo_org depends on org@
+i << r.i;
+j0 << ruletwo_context.j0;
+j2 << ruletwo_context.j2;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before break " % (i)
+coccilib.org.print_safe_todo(j0[0], msg)
+coccilib.org.print_link(j2[0], "")
+
+@script:python rulethree_org depends on org@
+i << r.i;
+j0 << rulethree_context.j0;
+j3 << rulethree_context.j3;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before goto " % (i)
+coccilib.org.print_safe_todo(j0[0], msg)
+coccilib.org.print_link(j3[0], "")
+
+// ----------------------------------------------------------------------------
+
+@script:python ruleone_report depends on report@
+i << r.i;
+j0 << ruleone_context.j0;
+j1 << ruleone_context.j1;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before return around line %s." % (i, j1[0].line)
+coccilib.report.print_report(j0[0], msg)
+
+@script:python ruletwo_report depends on report@
+i << r.i;
+j0 << ruletwo_context.j0;
+j2 << ruletwo_context.j2;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before break around line %s." % (i,j2[0].line)
+coccilib.report.print_report(j0[0], msg)
+
+@script:python rulethree_report depends on report@
+i << r.i;
+j0 << rulethree_context.j0;
+j3 << rulethree_context.j3;
+@@
+
+msg = "WARNING: Function \"%s\" should have of_node_put() before goto around lines %s." % (i,j3[0].line)
+coccilib.report.print_report(j0[0], msg)