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

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Len Baker <len.baker@gmx.com>
Link: https://lore.kernel.org/r/20210911112631.10004-1-len.baker@gmx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 1f5e69314a1723f1ba82f91136d1d90dc0eec067..666b1c6651881f5ff68b60c8f05a80ceae40f1c1 100644 (file)
--- 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);