linux-kernel - Re: [PATCH][next] usb: xhci-mtk: Use struct_size() helper in create_sch

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Date:   Thu, 20 Jan 2022 14:31:55 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>
CC:     <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH][next] usb: xhci-mtk: Use struct_size() helper in
 create_sch_ep()

On Wed, 2022-01-19 at 19:55 -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 worst scenario, could lead to heap overflows.
> 
> Also, address the following sparse warnings:
> drivers/usb/host/xhci-mtk-sch.c:265:20: 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>
> ---
>  drivers/usb/host/xhci-mtk-sch.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-
> mtk-sch.c
> index edbfa82c6565..f3139ce7b0a9 100644
> --- a/drivers/usb/host/xhci-mtk-sch.c
> +++ b/drivers/usb/host/xhci-mtk-sch.c
> @@ -248,7 +248,6 @@ create_sch_ep(struct xhci_hcd_mtk *mtk, struct
> usb_device *udev,
>  	struct mu3h_sch_bw_info *bw_info;
>  	struct mu3h_sch_tt *tt = NULL;
>  	u32 len_bw_budget_table;
> -	size_t mem_size;
>  
>  	bw_info = get_bw_info(mtk, udev, ep);
>  	if (!bw_info)
> @@ -262,9 +261,9 @@ create_sch_ep(struct xhci_hcd_mtk *mtk, struct
> usb_device *udev,
>  	else
>  		len_bw_budget_table = 1;
>  
> -	mem_size = sizeof(struct mu3h_sch_ep_info) +
> -			len_bw_budget_table * sizeof(u32);
> -	sch_ep = kzalloc(mem_size, GFP_KERNEL);
> +	sch_ep = kzalloc(struct_size(sch_ep, bw_budget_table,
> +				     len_bw_budget_table),
> +			 GFP_KERNEL);
>  	if (!sch_ep)
>  		return ERR_PTR(-ENOMEM);
Acked-by: Chunfeng Yun <chunfeng.yun@...iatek.com>

Thanks a lot

>