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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Pavel Skripkin' <paskripkin@gmail.com>
CC:     "Larry.Finger@lwfinger.net" <Larry.Finger@lwfinger.net>,
        "phil@philpotter.co.uk" <phil@philpotter.co.uk>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "straube.linux@gmail.com" <straube.linux@gmail.com>,
        "fmdefrancesco@gmail.com" <fmdefrancesco@gmail.com>,
        "linux-staging@lists.linux.dev" <linux-staging@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v3 3/6] staging: r8188eu: add error handling of rtw_read8
Thread-Topic: [PATCH v3 3/6] staging: r8188eu: add error handling of rtw_read8
Thread-Index: AQHXmLmGl/+E/B1vJUGWAidfG7snbKuFdLBA///xloCAAC/eAA==
Date:   Thu, 26 Aug 2021 10:19:40 +0000
Message-ID: <a251767ca181405b93b5ea55a26c3ff0@AcuMS.aculab.com>
References: <cover.1629789580.git.paskripkin@gmail.com>
        <c59d5d850bf9aab208704182c83086609289cb9c.1629789580.git.paskripkin@gmail.com>
        <f5c20e0f1b934e04ad11a3627d71f5db@AcuMS.aculab.com>
 <20210826112745.5e1421ed@gmail.com>
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From: Pavel Skripkin
> Sent: 26 August 2021 09:28
> 
> On Thu, 26 Aug 2021 08:21:34 +0000
> David Laight <David.Laight@ACULAB.COM> wrote:
> 
> > From: Pavel Skripkin
> > > Sent: 24 August 2021 08:27
> > >
> > > _rtw_read8 function can fail in case of usb transfer failure. But
> > > previous function prototype wasn't designed to return an error to
> > > caller. It can cause a lot uninit value bugs all across the driver
> > > code, since rtw_read8() returns local stack variable to caller.
> > >
> > > Fix it by changing the prototype of this function. Now it returns an
> > > int: 0 on success, negative error value on failure and callers
> > > should pass the pointer to storage location for register value.
> >
> > ...
> > > +		len += snprintf(page + len, count - len,
> > > "rtw_read8(0x%x)=0x%x\n",
> > > +				proc_get_read_addr, (u8) tmp);
> >
> > That is broken.
> >
> 
> Don't get it, sorry. Previous code did exactly the same thing, but
> didn't check if read() was successful.

Look up the return value of snprintf().

	David

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