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Wed, 9 Oct 2019 14:39:16 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 2vgefctcrq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 09 Oct 2019 14:39:16 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x99Ed5MH031000; Wed, 9 Oct 2019 14:39:05 GMT Received: from kadam (/41.57.98.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 09 Oct 2019 07:39:04 -0700 Date: Wed, 9 Oct 2019 17:38:55 +0300 From: Dan Carpenter To: Denis Efremov Cc: David Laight , "devel@driverdev.osuosl.org" , Jes Sorensen , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , Hans de Goede , Bastien Nocera , Dmitry Vyukov , Larry Finger Subject: Re: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls Message-ID: <20191009143855.GE13286@kadam> References: <20190930110141.29271-1-efremov@linux.com> <37b195b700394e95aa8329afc9f60431@AcuMS.aculab.com> <20191001135649.GH22609@kadam> <8d2e8196cae74ec4ae20e9c23e898207@AcuMS.aculab.com> <20191001185730.GM29696@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191001185730.GM29696@kadam> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9404 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910090140 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9404 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910090140 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 01, 2019 at 09:58:55PM +0300, Dan Carpenter wrote: > On Tue, Oct 01, 2019 at 06:13:21PM +0300, Denis Efremov wrote: > > Just found an official documentation to this issue: > > https://gcc.gnu.org/gcc-4.9/porting_to.html > > "Null pointer checks may be optimized away more aggressively > > ... > > The pointers passed to memmove (and similar functions in ) must be non-null > > even when nbytes==0, so GCC can use that information to remove the check after the > > memmove call. Calling copy(p, NULL, 0) can therefore deference a null pointer and crash." > > > > Correct. In glibc those functions are annotated as non-NULL. > > extern void *memcpy (void *__restrict __dest, const void *__restrict __src, > size_t __n) __THROW __nonnull ((1, 2)); I was wrong on this. It's built into GCC so it doesn't matter how it's annotated. > > We aren't going to do that in the kernel. A second difference is that > in the kernel we use -fno-delete-null-pointer-checks so it doesn't > delete the NULL checks. But it's true that the kernel has -fno-delete-null-pointer-checks so I don't think this is worth patching. regards, dan carpenter