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From:   Len Baker <len.baker@gmx.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>
Cc:     Len Baker <len.baker@gmx.com>, Kees Cook <keescook@chromium.org>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mario Kleiner <mario.kleiner.de@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Randy Wright <rwright@hpe.com>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Tobias Diedrich <tobiasdiedrich@gmail.com>,
        YueHaibing <yuehaibing@huawei.com>, linux-serial@vger.kernel.org,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] serial: 8250_pci: Prefer struct_size over open coded arithmetic
Date:   Sun,  5 Sep 2021 17:57:28 +0200
Message-Id: <20210905155728.11147-1-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 + size * count" 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/tty/serial/8250/8250_pci.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/=
8250_pci.c
index a808c283883e..b97ade35d4a3 100644
=2D-- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -3981,9 +3981,7 @@ pciserial_init_ports(struct pci_dev *dev, const stru=
ct pciserial_board *board)
 			nr_ports =3D rc;
 	}

-	priv =3D kzalloc(sizeof(struct serial_private) +
-		       sizeof(unsigned int) * nr_ports,
-		       GFP_KERNEL);
+	priv =3D kzalloc(struct_size(priv, line, nr_ports), GFP_KERNEL);
 	if (!priv) {
 		priv =3D ERR_PTR(-ENOMEM);
 		goto err_deinit;
=2D-
2.25.1