From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161639AbcHERXK (ORCPT ); Fri, 5 Aug 2016 13:23:10 -0400 Received: from mail-db5eur01on0048.outbound.protection.outlook.com ([104.47.2.48]:1312 "EHLO EUR01-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1161574AbcHERXG (ORCPT ); Fri, 5 Aug 2016 13:23:06 -0400 Authentication-Results: spf=pass (sender IP is 188.184.36.50) smtp.mailfrom=cern.ch; vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=bestguesspass action=none header.from=cern.ch; Subject: Re: kernel/printk/printk.c: Invalid access when buffer wraps around? To: Ivan Delalande References: <89c15437-5a97-68b1-d83f-097f3b047559@cern.ch> <20160801163328.GI26511@ycc.fr> CC: Andrew Morton , Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Kees Cook , Thierry Reding , Geliang Tang , Tejun Heo , From: Vincent Brillault Message-ID: <82e4f649-0e06-df57-d7ef-3f42bb633644@cern.ch> Date: Fri, 5 Aug 2016 07:14:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160801163328.GI26511@ycc.fr> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="LJQOg3ehVcdOpj2l8WinGUCBEKHSAwHli" X-Originating-IP: [90.42.189.131] X-EOPAttributedMessage: 0 X-Forefront-Antispam-Report: CIP:188.184.36.50;IPV:NLI;CTRY:CH;EFV:NLI;SFV:NSPM;SFS:(10009020)(6009001)(7916002)(2980300002)(438002)(199003)(52284002)(189002)(4326007)(92566002)(568964002)(2950100001)(19580405001)(19580395003)(189998001)(3846002)(6116002)(110136002)(586003)(21480400002)(512874002)(77096005)(2906002)(31686004)(87936001)(246002)(33646002)(5890100001)(7416002)(83506001)(345774005)(74482002)(76176999)(54356999)(50986999)(305945005)(4001350100001)(84326002)(7846002)(16796002)(7636002)(7736002)(8676002)(66066001)(65956001)(65806001)(5000100001)(8936002)(31696002)(64126003)(11100500001)(117156001)(36756003)(356003)(86362001)(106466001)(65826006);DIR:OUT;SFP:1101;SCL:1;SRVR:VI1PR0602MB2782;H:CERNMX11.cern.ch;FPR:;SPF:Pass;PTR:cernmx11.cern.ch;A:1;MX:1;LANG:en; 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boundary="HjJMUt2IUceFVdjjg3waW5kX256h299Q3" From: Vincent Brillault To: Ivan Delalande Cc: Andrew Morton , Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Kees Cook , Thierry Reding , Geliang Tang , Tejun Heo , linux-kernel@vger.kernel.org Message-ID: <82e4f649-0e06-df57-d7ef-3f42bb633644@cern.ch> Subject: Re: kernel/printk/printk.c: Invalid access when buffer wraps around? References: <89c15437-5a97-68b1-d83f-097f3b047559@cern.ch> <20160801163328.GI26511@ycc.fr> In-Reply-To: <20160801163328.GI26511@ycc.fr> --HjJMUt2IUceFVdjjg3waW5kX256h299Q3 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Dear Ivan, all Sorry for the delay, I currently have limited internet access. > Thanks for your very detailled write-up but I believe you are mistaken > on the value of log_first_idx between these two last steps you describe= =2E After re-reading log_next and log_make_free_space, I believe that you are right and that I was wrong. Your explanation is crystal-clear and I now don't understand how I missed this (it's even explained in the comments...). This means that we might be removing the first element in the buffer while there was enough space to store it at the end of the buffer, but I guess this is better than having a bug ;) I'm sorry for the noise everyone. Thank you for your patience and great explanation. Sincerely yours, Vincent Brillault --HjJMUt2IUceFVdjjg3waW5kX256h299Q3-- --LJQOg3ehVcdOpj2l8WinGUCBEKHSAwHli Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCgAGBQJXpCDGAAoJEM8JrGClGcyp5wkP/jM7TV18Vc0FBdr8RiTTywLN Lv+rCVKIwmH+em77xCmnpBdHKIsWOHKpS9/vN0rzizAeX0fAnNWT+Ib1zLBLXxEs RSKVirh9DJJB75nM/L79R/A7PSdGzN3CDwVySbTS24M63oFLEuiBJ440bzNbbt3F OmjFSqR7F8DcMFcfaCPiwhG+bJbq87MesSnmaLrQDIxm0Flj0z5UHbcICvvzHMvN RjFfV0lyF+6L1js9m8mCfcOHR1NXjNtUcdCsDRNHhtIE563d+Bo4Gl6yv/mS6m+i zbTOgcH2nvKzcjf41bMmuAFuV+clKqC5qGSj4KiZPoyT4VyE0CM4q0w4LYV7hvIg To+GWtrHJLN83OLFZM4WD2CgjXTbuY3kGyYw3pWd7OBJFZDVYWBQCdvI+bkczqVh n0/fWJZrd8Ua1MBsNTZ9Yw5rvOLEWMW0s5PuKAM/hcffC6VXXSoISVYmOdEZPskM aBk9ddNNtKW7fc0Z2l4eKjdgVcGa1kRCCR5IuJYpEI9/2pRSOSpnfl5fArVKpwo2 NWnlXD2EqD584yat3sr6POgXACwH2ccHMztqf62GeRvhXVBP42YhAAPPxJIrjzIT YUv2FZRdwqnQT7MdqRBVBFB7x4ZdaB0qAAevtScINGVLCV2qjhFeLdJJSJtbylFx FQinpC6DX/eq3GhqcEhk =tUqj -----END PGP SIGNATURE----- --LJQOg3ehVcdOpj2l8WinGUCBEKHSAwHli--