linux-hardening - [PATCH] Input: omap-keypad - prefer struct

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Message-Id: <20210911112716.10067-1-len.baker@gmx.com>
Date:   Sat, 11 Sep 2021 13:27:16 +0200
From:   Len Baker <len.baker@....com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Len Baker <len.baker@....com>, Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Input: omap-keypad - prefer struct_size 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.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@....com>
---
 drivers/input/keyboard/omap-keypad.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/omap-keypad.c b/drivers/input/keyboard/omap-keypad.c
index dbe836c7ff47..eb3a687796e7 100644
--- a/drivers/input/keyboard/omap-keypad.c
+++ b/drivers/input/keyboard/omap-keypad.c
@@ -190,8 +190,7 @@ static int omap_kp_probe(struct platform_device *pdev)
 	row_shift = get_count_order(pdata->cols);
 	keycodemax = pdata->rows << row_shift;

-	omap_kp = kzalloc(sizeof(struct omap_kp) +
-			keycodemax * sizeof(unsigned short), GFP_KERNEL);
+	omap_kp = kzalloc(struct_size(omap_kp, keymap, keycodemax), GFP_KERNEL);
 	input_dev = input_allocate_device();
 	if (!omap_kp || !input_dev) {
 		kfree(omap_kp);
--
2.25.1