linux-kernel - Re: [PATCH] USB: EHCI: fix dereference of ERR

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Message-ID: <55FF7014.3010903@linux.intel.com>
Date:	Mon, 21 Sep 2015 10:48:52 +0800
From:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH] USB: EHCI: fix dereference of ERR_PTR



On 09/16/2015 10:08 PM, Sudip Mukherjee wrote:
> On error find_tt() returns either a NULL pointer or the error value in
> ERR_PTR. But we were dereferencing it directly without even checking if
> find_tt() returned a valid pointer or not.
>
> Signed-off-by: Sudip Mukherjee <sudip@...torindia.org>
> ---
>   drivers/usb/host/ehci-sched.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
> index f9a3327..27bced7 100644
> --- a/drivers/usb/host/ehci-sched.c
> +++ b/drivers/usb/host/ehci-sched.c
> @@ -257,6 +257,8 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
>   	/* FS/LS bus bandwidth */
>   	if (tt_usecs) {
>   		tt = find_tt(qh->ps.udev);
> +		if (!tt || IS_ERR(tt))

Why not IS_ERR_OR_NULL()?

> +			return;
>   		if (sign > 0)
>   			list_add_tail(&qh->ps.ps_list, &tt->ps_list);
>   		else
> @@ -1373,6 +1375,8 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
>   		}
>   
>   		tt = find_tt(stream->ps.udev);
> +		if (!tt || IS_ERR(tt))
> +			return;
>   		if (sign > 0)
>   			list_add_tail(&stream->ps.ps_list, &tt->ps_list);
>   		else

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