netdev - [PATCH] net: mana: Prefer struct_size over open coded arithmetic

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Message-Id: <20210911102818.3804-1-len.baker@gmx.com>
Date:   Sat, 11 Sep 2021 12:28:18 +0200
From:   Len Baker <len.baker@....com>
To:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Kees Cook <keescook@...omium.org>
Cc:     Len Baker <len.baker@....com>,
        Colin Ian King <colin.king@...onical.com>,
        linux-hardening@...r.kernel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: [PATCH] net: mana: 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/net/ethernet/microsoft/mana/hw_channel.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
index 1a923fd99990..0efdc6c3c32a 100644
--- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
+++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
@@ -398,9 +398,7 @@ static int mana_hwc_alloc_dma_buf(struct hw_channel_context *hwc, u16 q_depth,
 	int err;
 	u16 i;

-	dma_buf = kzalloc(sizeof(*dma_buf) +
-			  q_depth * sizeof(struct hwc_work_request),
-			  GFP_KERNEL);
+	dma_buf = kzalloc(struct_size(dma_buf, reqs, q_depth), GFP_KERNEL);
 	if (!dma_buf)
 		return -ENOMEM;

--
2.25.1