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Fri, 16 Apr 2021 08:09:54 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 13G80gTT002449; Fri, 16 Apr 2021 08:09:53 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 37unkttprp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 16 Apr 2021 08:09:52 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 13G89oV9006168; Fri, 16 Apr 2021 08:09:50 GMT Received: from kadam (/102.36.221.92) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 16 Apr 2021 01:09:50 -0700 Date: Fri, 16 Apr 2021 11:09:41 +0300 From: Dan Carpenter To: Christophe Leroy Subject: Re: [PATCH] powerpc: Initialize local variable fdt to NULL in elf64_load() Message-ID: <20210416080941.GO6048@kadam> References: <20210415191437.20212-1-nramas@linux.microsoft.com> <4edb1433-4d1e-5719-ec9c-fd232b7cf71f@linux.microsoft.com> <87eefag241.fsf@linkitivity.dja.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-IMR: 1 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9955 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999 adultscore=0 phishscore=0 malwarescore=0 mlxscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104160060 X-Proofpoint-GUID: 6HXQ_LEuwfVp63QXRqzWQcS2rPDaKaDw X-Proofpoint-ORIG-GUID: 6HXQ_LEuwfVp63QXRqzWQcS2rPDaKaDw X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9955 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 priorityscore=1501 clxscore=1011 adultscore=0 mlxlogscore=999 impostorscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 phishscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104160061 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, kbuild-all@lists.01.org, lkp@intel.com, robh@kernel.org, Lakshmi Ramasubramanian , linuxppc-dev , bauerman@linux.ibm.com, Daniel Axtens Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Apr 16, 2021 at 09:00:12AM +0200, Christophe Leroy wrote: > > > Le 16/04/2021 à 08:44, Daniel Axtens a écrit : > > Hi Lakshmi, > > > > > On 4/15/21 12:14 PM, Lakshmi Ramasubramanian wrote: > > > > > > Sorry - missed copying device-tree and powerpc mailing lists. > > > > > > > There are a few "goto out;" statements before the local variable "fdt" > > > > is initialized through the call to of_kexec_alloc_and_setup_fdt() in > > > > elf64_load(). This will result in an uninitialized "fdt" being passed > > > > to kvfree() in this function if there is an error before the call to > > > > of_kexec_alloc_and_setup_fdt(). > > > > > > > > Initialize the local variable "fdt" to NULL. > > > > > > I'm a huge fan of initialising local variables! But I'm struggling to > > find the code path that will lead to an uninit fdt being returned... > > > > The out label reads in part: > > > > /* Make kimage_file_post_load_cleanup free the fdt buffer for us. */ > > return ret ? ERR_PTR(ret) : fdt; > > > > As far as I can tell, any time we get a non-zero ret, we're going to > > return an error pointer rather than the uninitialised value... > > I don't think GCC is smart enough to detect that. > We disabled uninitialized variable checking for GCC. But actually is something that has been on my mind recently. Smatch is supposed to parse this correctly but there is a bug that affects powerpc and I don't know how to debug it. The kbuild bot is doing cross platform compiles but I don't have one set up on myself. Could someone with Smatch installed test something for me? Or if you don't have Smatch installed then you should definitely install it. :P https://www.spinics.net/lists/smatch/msg00568.html Apply the patch from below and edit the path to point to the correct directory. Then run kchecker and email me the output? ~/path/to/smatch_scripts/kchecker arch/powerpc/kernel/hw_breakpoint.c regads, dan carpenter diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index 8fc7a14e4d71..f2dfba54e14d 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -167,13 +167,19 @@ static bool can_co_exist(struct breakpoint *b, struct perf_event *bp) return !(alternate_infra_bp(b, bp) && bp_addr_range_overlap(b->bp, bp)); } +#include "/home/XXX/path/to/smatch/check_debug.h" static int task_bps_add(struct perf_event *bp) { struct breakpoint *tmp; tmp = alloc_breakpoint(bp); - if (IS_ERR(tmp)) + __smatch_about(tmp); + __smatch_debug_on(); + if (IS_ERR(tmp)) { + __smatch_debug_off(); + __smatch_about(tmp); return PTR_ERR(tmp); + } list_add(&tmp->list, &task_bps); return 0;