linux-kernel - [PATCH] Coccinelle: misc: Add SmPL script “show_questionable_count_limit

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Message-ID: <30a3a2b1-deef-4f3f-b7da-4164360190ed@web.de>
Date: Sat, 5 Jul 2025 22:05:44 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: cocci@...ia.fr, kernel-janitors@...r.kernel.org,
 Julia Lawall <Julia.Lawall@...ia.fr>, Nicolas Palix <nicolas.palix@...g.fr>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] Coccinelle: misc: Add SmPL script “show_questionable_count_limit_checks.cocci”

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Sat, 5 Jul 2025 21:46:23 +0200

Some known programming mistakes are repeated.

See also:
* https://lore.kernel.org/all/?q=%22Fix+off+by+one%22

* https://wiki.sei.cmu.edu/confluence/display/c/ARR30-C.+Do+not+form+or+use+out-of-bounds+pointers+or+array+subscripts


Thus provide design options for the adjustment of affected source code
also by the means of the semantic patch language (Coccinelle software).

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---

A parse check for the operation mode “report” provides the following hint.

“…
Grep query
for
…”

It seems that such a key word tends to occur in a lot of source files.
Thus this source code search pattern will probably trigger the demand for
special computation resources.
I became curious on corresponding collateral evolution.


 ...show_questionable_count_limit_checks.cocci | 72 +++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 scripts/coccinelle/misc/show_questionable_count_limit_checks.cocci

diff --git a/scripts/coccinelle/misc/show_questionable_count_limit_checks.cocci b/scripts/coccinelle/misc/show_questionable_count_limit_checks.cocci
new file mode 100644
index 000000000000..d565e306711f
--- /dev/null
+++ b/scripts/coccinelle/misc/show_questionable_count_limit_checks.cocci
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/// Reconsider questionable count limit checks.
+//
+// Keywords: detection programming mistakes
+// Confidence: Medium
+// Options: --no-includes --include-headers
+
+virtual context, patch, report, org
+
+@...ends on context@
+expression limit;
+identifier i;
+statement s;
+@@
+ for (
+      <+... i = 0 ...+> ;
+*     i <= limit
+      ;
+      <+...
+(     i++
+|     ++i
+)     ...+>
+     )
+ s
+
+@...ends on patch disable gtr_lss_eq@
+expression limit;
+identifier i;
+statement s;
+@@
+ for (
+      <+... i = 0 ...+> ;
+(
+-     i <= limit
++     i < limit
+|
+-     limit >= i
++     limit > i
+)     ;
+      <+...
+(     i++
+|     ++i
+)     ...+>
+     )
+ s
+
+@x depends on org || report@
+expression limit;
+identifier i;
+position p;
+statement s;
+@@
+ for (
+      <+... i = 0 ...+> ;
+      i <= limit
+      ;@p
+      <+...
+(     i++
+|     ++i
+)     ...+>
+     )
+ s
+
+@...ipt:python depends on org@
+p << x.p;
+@@
+coccilib.org.print_todo(p[0], "WARNING: Reconsider questionable count limit check once more.")
+
+@...ipt:python depends on report@
+p << x.p;
+@@
+coccilib.report.print_report(p[0], "WARNING: Reconsider questionable count limit check once more.")
-- 
2.50.0