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

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Message-ID: <20150921044947.GA6962@sudip-pc>
Date:	Mon, 21 Sep 2015 10:19:50 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH] USB: EHCI: fix dereference of ERR_PTR

On Mon, Sep 21, 2015 at 10:48:52AM +0800, Lu, Baolu wrote:
> 
> 
> 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()?
This was v1, corrected in v2. And Alan has already explained why this
patch is not required.

regards
sudip
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