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

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Date: Sat, 20 Jan 2024 13:05:27 +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>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Erick Archer <erick.archer@....com>,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] 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.

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>
---
 Documentation/power/opp.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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))) {
--
2.25.1