linux-kernel - [PATCH] usb: ohci: Prefer struct_size over open coded arithmetic

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Message-Id: <20210911112631.10004-1-len.baker@gmx.com>
Date:   Sat, 11 Sep 2021 13:26:31 +0200
From:   Len Baker <len.baker@....com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Len Baker <len.baker@....com>, Kees Cook <keescook@...omium.org>,
        linux-usb@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] usb: ohci: 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/usb/host/ohci-hcd.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 1f5e69314a17..666b1c665188 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/drivers/usb/host/ohci-hcd.c
@@ -191,8 +191,7 @@ static int ohci_urb_enqueue (
 	}

 	/* allocate the private part of the URB */
-	urb_priv = kzalloc (sizeof (urb_priv_t) + size * sizeof (struct td *),
-			mem_flags);
+	urb_priv = kzalloc(struct_size(urb_priv, td, size), mem_flags);
 	if (!urb_priv)
 		return -ENOMEM;
 	INIT_LIST_HEAD (&urb_priv->pending);
--
2.25.1