From: Alan Stern <stern@rowland.harvard.edu>
To: Len Baker <len.baker@gmx.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>,
linux-usb@vger.kernel.org, linux-hardening@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: ohci: Prefer struct_size over open coded arithmetic
Date: Sat, 11 Sep 2021 11:46:48 -0400 [thread overview]
Message-ID: <20210911154648.GA68944@rowland.harvard.edu> (raw)
In-Reply-To: <20210911112631.10004-1-len.baker@gmx.com>
On Sat, Sep 11, 2021 at 01:26:31PM +0200, Len Baker wrote:
> 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@gmx.com>
> ---
Acked-by: Alan Stern <stern@rowland.harvard.edu>
> 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
>
prev parent reply other threads:[~2021-09-11 15:46 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-11 11:26 [PATCH] usb: ohci: Prefer struct_size over open coded arithmetic Len Baker
2021-09-11 15:46 ` Alan Stern [this message]
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