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bh=r2Yj7B17/HcvuSi4RES9kwNBsaNmZIzyyL2RvE/u4og=; b=YP5ziLwbh6n3U3OwxziFcnpMzIq/ivX+McyjfQg7DTf8cn1jp4nSm2D2/5XU3C0tOMU3g3ytPPsYYxz2Y4O09LnWbk81oEQ93PxLsqIUQTe185kC6u3QArsDUWyfKzbl2lAbypsQU0PGI3mQRpq5nRL7ilavBZ8YIz3iJwlHwP8= Date: Thu, 10 Mar 2022 16:39:18 +0300 To: Joseph Qi Message-id: <20220310133918.GH3315@kadam> References: <20220307145138.GA22641@kili> <82b26a4a-2351-f2b3-dd7c-265308e6b384@gmail.com> <20220309145717.GX3315@kadam> <5a5933bb-3078-2cfa-9403-a6b497199449@linux.alibaba.com> Content-disposition: inline In-reply-to: <5a5933bb-3078-2cfa-9403-a6b497199449@linux.alibaba.com> User-Agent: Mutt/1.9.4 (2018-02-28) MIME-version: 1.0 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:-1; SRV:; IPV:NLI; SFV:SKI; H:MWHPR1001MB2365.namprd10.prod.outlook.com; PTR:; CAT:NONE; SFS:; DIR:INB; X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Mar 2022 13:39:30.2985 (UTC) X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10281 signatures=692062 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 spamscore=0 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203100073 Cc: Jakob Koschel , ocfs2-devel@oss.oracle.com Subject: Re: [Ocfs2-devel] [bug report] ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Dan Carpenter via Ocfs2-devel Reply-to: Dan Carpenter Content-type: text/plain; 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SFV:SKI; SKIP:0; X-MS-Exchange-CrossPremises-SCL: -1 X-MS-Exchange-CrossPremises-Processed-By-Journaling: Journal Agent X-OrganizationHeadersPreserved: BN6PR10MB1508.namprd10.prod.outlook.com X-Proofpoint-ORIG-GUID: ah0hLfZd5jbcm_7YlSyLXtMppZIXKBsp X-Proofpoint-GUID: ah0hLfZd5jbcm_7YlSyLXtMppZIXKBsp Reporting-Meta: AAGcTKyNyeR13zdoDKXRoRo5u6iHtUoprVV+7CNW040vf8YUt89tEuiL8EB7MOzV U5mvTS0bYRNtueCYX0NGvNAdFy0yL8keOLixSaTKxFqkhmiy2YWOgHFIAdEhmkjk Ed/jEjfhFXe8EObCTw3znWVOYyYKWj/RM+Oct0zctk4tbbaiVK3LmY6g7fHrzAzt Qt7hBEtD1Jm5Y/iOdHLqNnQ1MxBhA/023OSKujWIufTC6RgeaUKyxPHNWoD95iqx rAgMcj6QCL802pMAYfdgQRV9G9ynrzKIkrKbM3l/8BDAQllDAYpPpQ6iLFLdJwbA xe2hxrBcJR9aWqoJu1NGsV+w89pVHbKpACcVHBAudJiSQjb92//6vTcKZOrxuI8v 3R486d8eCyy146hEPdHWqpPlhl0J5PIYjfvx1+KKD4J1uvdAS11XpDH7y+4w+HXD bhE6mKt1YlQs1/3xxbUAa/WQYCILYWkC/2NBwicw1xq9uTE+d07nmcqmK1tlKYzR 4o5c94AzSRZS2yGl1LHlK2hp3nv1uS3zRyJGL2gdMYuRNQ== On Thu, Mar 10, 2022 at 11:13:05AM +0800, Joseph Qi wrote: > >>> 557 } > >>> 558 > >>> 559 list_for_each_entry(res, track_list, tracking) { > >>> 560 if (&res->tracking == &dlm->tracking_list) > >>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>> This should never be possible. How is it possible? If > >>> &dlm->tracking_list is the list head the it's not possible without > >>> memory corruption. If &oldres->tracking is the list head then I do not > >>> see how it is possible without memory corruption. We can't mix different > >>> types of list entries on the same list head?> > >> In case of oldres, and the iterator points to dlm_ctxt. > >> In this case, the lockres is not a valid one. > > > > That doesn't make sense. :/ This condition is doing pointer math. > > The offset of ->tracking is 136 bytes and ->tracking list is 88 bytes > > into the dlm struct. > > > Now track_list is oldres->tracking, which is already linked to > dlm->tracking_list? Are you saying or are you guessing? :P It's not impossible to set this condition up so that it's true. But it's bug if someone does that. I really think that condition can be deleted. If you look at the commit which added it b0d4f817ba5d ("ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list") the it's easy to imagine that it was a copy and pasted pasted by mistake. Or another possibility is that it was debug code that was committed accidentally. After all if you remove the locking a delete the last entry at the right time then it would be easy enough for the condition to be true. Hopefully, these days the locking prevents that condition from being possible. regards, dan carpenter _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel