linux-kernel - Re: [PATCH][next] usb: host: ehci-sched: Use struct

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Message-ID: <Yd3KGMSb7vBIwH+j@rowland.harvard.edu>
Date:   Tue, 11 Jan 2022 13:19:04 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] usb: host: ehci-sched: Use struct_size() in
 kzalloc()

On Tue, Jan 11, 2022 at 01:54:27AM -0600, Gustavo A. R. Silva wrote:
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worse scenario, could lead to heap overflows.
> 
> Also, address the following sparse warning:
> drivers/usb/host/ehci-sched.c:1168:40: warning: using sizeof on a flexible structure
> 
> Link: https://github.com/KSPP/linux/issues/160
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---

Acked-by: Alan Stern <stern@...land.harvard.edu>

>  drivers/usb/host/ehci-sched.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
> index 0f85aa9b2fb1..bd542b6fc46b 100644
> --- a/drivers/usb/host/ehci-sched.c
> +++ b/drivers/usb/host/ehci-sched.c
> @@ -1165,10 +1165,8 @@ static struct ehci_iso_sched *
>  iso_sched_alloc(unsigned packets, gfp_t mem_flags)
>  {
>  	struct ehci_iso_sched	*iso_sched;
> -	int			size = sizeof(*iso_sched);
>  
> -	size += packets * sizeof(struct ehci_iso_packet);
> -	iso_sched = kzalloc(size, mem_flags);
> +	iso_sched = kzalloc(struct_size(iso_sched, packet, packets), mem_flags);
>  	if (likely(iso_sched != NULL))
>  		INIT_LIST_HEAD(&iso_sched->td_list);
>  
> -- 
> 2.27.0
>