linux-kernel - [PATCH] hwmon: submitting-patches: Explain race conditions caused by calculations in macros

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251202175536.12774-1-hanguidong02@gmail.com>
Date: Wed,  3 Dec 2025 01:55:36 +0800
From: Gui-Dong Han <hanguidong02@...il.com>
To: linux@...ck-us.net
Cc: linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	baijiaju1990@...il.com,
	Gui-Dong Han <hanguidong02@...il.com>
Subject: [PATCH] hwmon: submitting-patches: Explain race conditions caused by calculations in macros

The current documentation advises against calculations in macros
primarily to avoid code obfuscation. It misses the risk of concurrency
issues.

Add a note explaining that macros evaluating arguments multiple times
can lead to race conditions when accessing shared data.

Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/
Signed-off-by: Gui-Dong Han <hanguidong02@...il.com>
---
 Documentation/hwmon/submitting-patches.rst | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Documentation/hwmon/submitting-patches.rst b/Documentation/hwmon/submitting-patches.rst
index 6482c4f137dc..7f7095951750 100644
--- a/Documentation/hwmon/submitting-patches.rst
+++ b/Documentation/hwmon/submitting-patches.rst
@@ -82,7 +82,10 @@ increase the chances of your change being accepted.
 * Avoid calculations in macros and macro-generated functions. While such macros
   may save a line or so in the source, it obfuscates the code and makes code
   review more difficult. It may also result in code which is more complicated
-  than necessary. Use inline functions or just regular functions instead.
+  than necessary. Such macros may also evaluate their arguments multiple times.
+  This leads to Time-of-Check to Time-of-Use (TOCTOU) race conditions when
+  accessing shared data without locking, for example when calculating values in
+  sysfs show functions. Use inline functions or just regular functions instead.
 
 * Limit the number of kernel log messages. In general, your driver should not
   generate an error message just because a runtime operation failed. Report
-- 
2.43.0