linux-kernel - Re: [PATCH][next] USB: EHCI: ehci-mv: fix less than zero comparisonof an unsigned int

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Date:   Fri, 15 May 2020 21:17:11 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Tang Bin <tangbin@...s.chinamobile.com>
Cc:     Colin King <colin.king@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Zhang Shengju <zhangshengju@...s.chinamobile.com>,
        linux-usb@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] USB: EHCI: ehci-mv: fix less than zero
 comparisonof an unsigned int

On Sat, May 16, 2020 at 07:23:42AM +0800, Tang Bin wrote:
> Hi Alan & Colin：
> 
> On 2020/5/16 1:21, Alan Stern wrote:
> > On Fri, May 15, 2020 at 05:54:53PM +0100, Colin King wrote:
> > > From: Colin Ian King <colin.king@...onical.com>
> > > 
> > > The comparison of hcd->irq to less than zero for an error check will
> > > never be true because hcd->irq is an unsigned int.  Fix this by
> > > assigning the int retval to the return of platform_get_irq and checking
> > > this for the -ve error condition and assigning hcd->irq to retval.
> > > 
> > > Addresses-Coverity: ("Unsigned compared against 0")
> > > Fixes: c856b4b0fdb5 ("USB: EHCI: ehci-mv: fix error handling in mv_ehci_probe()")
> > > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > > ---
> > Thanks to Coverity for spotting this.  Any reason why it didn't spot
> > exactly the same mistake in the ohci-da8xx.c driver?
> 
> I just looked at the code and wondered whether it would be more appropriate
> to modify the header file "hcd.h".  Since 'irq' might be an negative, why
> not just modify the variables in the 'struct usb_hcd',  'unsigned int 
> irq'--> 'int irq'? After all, it's a public one.

I think the code in the drivers should be changed.  The reason is if 
platform_get_irq() returns a negative value, then that value should be 
what the probe function returns.

Alan Stern