linux-hardening - [PATCH v2 3/3] staging/rtl8192u: Prefer kcalloc over open coded arithmetic

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Date:   Tue, 24 Aug 2021 11:00:39 +0200
From:   Len Baker <len.baker@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Len Baker <len.baker@....com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Michael Straube <straube.linux@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2 3/3] staging/rtl8192u: Prefer kcalloc over open coded
 arithmetic

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.

In this case these aren't actually dynamic sizes: both sides of the
multiplication are constant values. However it is best to refactor these
anyway, just to keep the open-coded math idiom out of code.

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

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Len Baker <len.baker@....com>
---
 drivers/staging/rtl8192u/r819xU_phy.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/rtl8192u/r819xU_phy.c b/drivers/staging/rtl8192u/r819xU_phy.c
index ff6fe2ee3349..97f4d89500ae 100644
--- a/drivers/staging/rtl8192u/r819xU_phy.c
+++ b/drivers/staging/rtl8192u/r819xU_phy.c
@@ -1195,17 +1195,17 @@ static u8 rtl8192_phy_SwChnlStepByStep(struct net_device *dev, u8 channel,
 	u8 e_rfpath;
 	bool ret;

-	pre_cmd = kzalloc(sizeof(*pre_cmd) * MAX_PRECMD_CNT, GFP_KERNEL);
+	pre_cmd = kcalloc(MAX_PRECMD_CNT, sizeof(*pre_cmd), GFP_KERNEL);
 	if (!pre_cmd)
 		return false;

-	post_cmd = kzalloc(sizeof(*post_cmd) * MAX_POSTCMD_CNT, GFP_KERNEL);
+	post_cmd = kcalloc(MAX_POSTCMD_CNT, sizeof(*post_cmd), GFP_KERNEL);
 	if (!post_cmd) {
 		kfree(pre_cmd);
 		return false;
 	}

-	rf_cmd = kzalloc(sizeof(*rf_cmd) * MAX_RFDEPENDCMD_CNT, GFP_KERNEL);
+	rf_cmd = kcalloc(MAX_RFDEPENDCMD_CNT, sizeof(*rf_cmd), GFP_KERNEL);
 	if (!rf_cmd) {
 		kfree(pre_cmd);
 		kfree(post_cmd);
--
2.25.1