linux-kernel - [PATCH v2] Documentation: power: Use kcalloc() instead of kzalloc()

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Date: Sun, 21 Jan 2024 11:43:44 +0100
From: Erick Archer <erick.archer@....com>
To: Viresh Kumar <vireshk@...nel.org>,
	Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	Alex Shi <alexs@...nel.org>,
	Yanteng Si <siyanteng@...ngson.cn>,
	Jonathan Corbet <corbet@....net>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Hu Haowen <2023002089@...k.tyut.edu.cn>
Cc: Erick Archer <erick.archer@....com>,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2] Documentation: power: Use kcalloc() instead of kzalloc()

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, in the example code use the purpose specific kcalloc() function
instead of the argument size * count in the kzalloc() function.

At the same time, modify the translations accordingly.

Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/162
Signed-off-by: Erick Archer <erick.archer@....com>
---
Hi,

This patch is a merger of two previous ones [1] [2].
As Hu Haowen and Jonathan Corbet suggested, the translation change
only makes sense if the original file is modified. So, with this
v2 version the original file and the translations are modified at
the same time.

[1] https://lore.kernel.org/linux-hardening/20240120120527.3866-1-erick.archer@gmx.com/
[2] https://lore.kernel.org/linux-hardening/20240120122204.4287-1-erick.archer@gmx.com/

Thanks,
Erick
---
 Documentation/power/opp.rst                    | 2 +-
 Documentation/translations/zh_CN/power/opp.rst | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/power/opp.rst b/Documentation/power/opp.rst
index a7c03c470980..1b7f1d854f14 100644
--- a/Documentation/power/opp.rst
+++ b/Documentation/power/opp.rst
@@ -305,7 +305,7 @@ dev_pm_opp_get_opp_count
 	 {
 		/* Do things */
 		num_available = dev_pm_opp_get_opp_count(dev);
-		speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
+		speeds = kcalloc(num_available, sizeof(u32), GFP_KERNEL);
 		/* populate the table in increasing order */
 		freq = 0;
 		while (!IS_ERR(opp = dev_pm_opp_find_freq_ceil(dev, &freq))) {
diff --git a/Documentation/translations/zh_CN/power/opp.rst b/Documentation/translations/zh_CN/power/opp.rst
index 8d6e3f6f6202..7470fa2d4c43 100644
--- a/Documentation/translations/zh_CN/power/opp.rst
+++ b/Documentation/translations/zh_CN/power/opp.rst
@@ -274,7 +274,7 @@ dev_pm_opp_get_opp_count
 	 {
 		/* 做一些事情 */
 		num_available = dev_pm_opp_get_opp_count(dev);
-		speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
+		speeds = kcalloc(num_available, sizeof(u32), GFP_KERNEL);
 		/* 按升序填充表 */
 		freq = 0;
 		while (!IS_ERR(opp = dev_pm_opp_find_freq_ceil(dev, &freq))) {
--
2.25.1