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From:   Len Baker <len.baker@gmx.com>
To:     Simon Horman <simon.horman@corigine.com>,
        Jakub Kicinski <kuba@kernel.org>,
        "David S. Miller" <davem@davemloft.net>
Cc:     Len Baker <len.baker@gmx.com>, Kees Cook <keescook@chromium.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        oss-drivers@corigine.com, netdev@vger.kernel.org,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] nfp: Prefer struct_size over open coded arithmetic
Date:   Sun, 12 Sep 2021 15:10:57 +0200
Message-Id: <20210912131057.2285-1-len.baker@gmx.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

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-cod=
ed-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
=2D--
 drivers/net/ethernet/netronome/nfp/nfp_net_repr.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c b/drivers/n=
et/ethernet/netronome/nfp/nfp_net_repr.c
index 3b8e675087de..369f6ae700c7 100644
=2D-- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
@@ -499,8 +499,7 @@ struct nfp_reprs *nfp_reprs_alloc(unsigned int num_rep=
rs)
 {
 	struct nfp_reprs *reprs;

-	reprs =3D kzalloc(sizeof(*reprs) +
-			num_reprs * sizeof(struct net_device *), GFP_KERNEL);
+	reprs =3D kzalloc(struct_size(reprs, reprs, num_reprs), GFP_KERNEL);
 	if (!reprs)
 		return NULL;
 	reprs->num_reprs =3D num_reprs;
=2D-
2.25.1