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Thu, 24 Sep 2020 23:18:47 -0800 Received: from MTKMBS01N2.mediatek.inc (172.21.101.79) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 25 Sep 2020 00:18:45 -0700 Received: from mtkcas08.mediatek.inc (172.21.101.126) by mtkmbs01n2.mediatek.inc (172.21.101.79) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 25 Sep 2020 15:18:42 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas08.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 25 Sep 2020 15:18:43 +0800 Message-ID: <1601018323.28162.4.camel@mtksdccf07> Subject: Re: [PATCH v4 1/6] timer: kasan: record timer stack From: Walter Wu To: Thomas Gleixner Date: Fri, 25 Sep 2020 15:18:43 +0800 In-Reply-To: <87h7rm97js.fsf@nanos.tec.linutronix.de> References: <20200924040335.30934-1-walter-zh.wu@mediatek.com> <87h7rm97js.fsf@nanos.tec.linutronix.de> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 3C3089F7FF02F5E21612A0E8793CCC1F5A4AAE300078785DD5266310F77958DD2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200925_031859_197625_FBF88757 X-CRM114-Status: GOOD ( 22.03 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marco Elver , wsd_upstream , Stephen Boyd , Alexander Potapenko , linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, John Stultz , linux-arm-kernel@lists.infradead.org, Andrey Konovalov , Matthias Brugger , Andrey Ryabinin , Andrew Morton , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On Thu, 2020-09-24 at 23:41 +0200, Thomas Gleixner wrote: > On Thu, Sep 24 2020 at 12:03, Walter Wu wrote: > > When analyze use-after-free or double-free issue, recording the timer > > stacks is helpful to preserve usage history which potentially gives > > a hint about the affected code. > > > > Record the most recent two timer init calls in KASAN which are printed > > on failure in the KASAN report. > > > > For timers it has turned out to be useful to record the stack trace > > of the timer init call. > > In which way? And what kind of bug does it catch which cannot be catched > by existing debug mechanisms already? > We only provide another debug mechanisms to debug use-after-free or double-free, it can be displayed together in KASAN report and have a chance to debug, and it doesn't need to enable existing debug mechanisms at the same time. then it has a chance to resolve issue. > > Because if the UAF root cause is in timer init, then user can see > > KASAN report to get where it is registered and find out the root > > cause. > > What? If the UAF root cause is in timer init, then registering it after > using it in that very same function is pretty pointless. > See [1], the call stack shows UAF happen at dummy_timer(), it is the callback function and set by timer_setup(), if KASAN report shows the timer call stack, it should be useful for programmer. [1] https://syzkaller.appspot.com/bug?id=34e69b7c8c0165658cbc987da0b61dadec644b6b > > It don't need to enable DEBUG_OBJECTS_TIMERS, but they have a chance > > to find out the root cause. > > There is a lot of handwaving how useful this is, but TBH I don't see the > value at all. > > DEBUG_OBJECTS_TIMERS does a lot more than crashing on UAF. If KASAN > provides additional value over DEBUG_OBJECTS_TIMERS then spell it out, > but just saying that you don't need to enable DEBUG_OBJECTS_TIMERS is > not making an argument for that change. > We don't want to replace DEBUG_OBJECTS_TIMERS with this patches, only hope to use low overhead(compare with DEBUG_OBJECTS_TIMERS) to debug use-after-free/double-free issue. If you have some concerns, we can add those message into commit log. Thanks. Walter _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1396DC4363D for ; Fri, 25 Sep 2020 07:20:26 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 826BE23447 for ; 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Fri, 25 Sep 2020 15:18:43 +0800 Message-ID: <1601018323.28162.4.camel@mtksdccf07> Subject: Re: [PATCH v4 1/6] timer: kasan: record timer stack From: Walter Wu To: Thomas Gleixner Date: Fri, 25 Sep 2020 15:18:43 +0800 In-Reply-To: <87h7rm97js.fsf@nanos.tec.linutronix.de> References: <20200924040335.30934-1-walter-zh.wu@mediatek.com> <87h7rm97js.fsf@nanos.tec.linutronix.de> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 3C3089F7FF02F5E21612A0E8793CCC1F5A4AAE300078785DD5266310F77958DD2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200925_031859_197625_FBF88757 X-CRM114-Status: GOOD ( 22.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marco Elver , wsd_upstream , Stephen Boyd , Alexander Potapenko , linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, John Stultz , linux-arm-kernel@lists.infradead.org, Andrey Konovalov , Matthias Brugger , Andrey Ryabinin , Andrew Morton , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 2020-09-24 at 23:41 +0200, Thomas Gleixner wrote: > On Thu, Sep 24 2020 at 12:03, Walter Wu wrote: > > When analyze use-after-free or double-free issue, recording the timer > > stacks is helpful to preserve usage history which potentially gives > > a hint about the affected code. > > > > Record the most recent two timer init calls in KASAN which are printed > > on failure in the KASAN report. > > > > For timers it has turned out to be useful to record the stack trace > > of the timer init call. > > In which way? And what kind of bug does it catch which cannot be catched > by existing debug mechanisms already? > We only provide another debug mechanisms to debug use-after-free or double-free, it can be displayed together in KASAN report and have a chance to debug, and it doesn't need to enable existing debug mechanisms at the same time. then it has a chance to resolve issue. > > Because if the UAF root cause is in timer init, then user can see > > KASAN report to get where it is registered and find out the root > > cause. > > What? If the UAF root cause is in timer init, then registering it after > using it in that very same function is pretty pointless. > See [1], the call stack shows UAF happen at dummy_timer(), it is the callback function and set by timer_setup(), if KASAN report shows the timer call stack, it should be useful for programmer. [1] https://syzkaller.appspot.com/bug?id=34e69b7c8c0165658cbc987da0b61dadec644b6b > > It don't need to enable DEBUG_OBJECTS_TIMERS, but they have a chance > > to find out the root cause. > > There is a lot of handwaving how useful this is, but TBH I don't see the > value at all. > > DEBUG_OBJECTS_TIMERS does a lot more than crashing on UAF. If KASAN > provides additional value over DEBUG_OBJECTS_TIMERS then spell it out, > but just saying that you don't need to enable DEBUG_OBJECTS_TIMERS is > not making an argument for that change. > We don't want to replace DEBUG_OBJECTS_TIMERS with this patches, only hope to use low overhead(compare with DEBUG_OBJECTS_TIMERS) to debug use-after-free/double-free issue. If you have some concerns, we can add those message into commit log. Thanks. Walter _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BDF2C4363D for ; Fri, 25 Sep 2020 07:18:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5478D2311B for ; Fri, 25 Sep 2020 07:18:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="ojRsscfI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5478D2311B Authentication-Results: mail.kernel.org; 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Fri, 25 Sep 2020 15:18:42 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas08.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 25 Sep 2020 15:18:43 +0800 Message-ID: <1601018323.28162.4.camel@mtksdccf07> Subject: Re: [PATCH v4 1/6] timer: kasan: record timer stack From: Walter Wu To: Thomas Gleixner CC: Andrew Morton , John Stultz , Stephen Boyd , Marco Elver , Andrey Ryabinin , "Alexander Potapenko" , Dmitry Vyukov , "Andrey Konovalov" , Matthias Brugger , , , , , wsd_upstream , Date: Fri, 25 Sep 2020 15:18:43 +0800 In-Reply-To: <87h7rm97js.fsf@nanos.tec.linutronix.de> References: <20200924040335.30934-1-walter-zh.wu@mediatek.com> <87h7rm97js.fsf@nanos.tec.linutronix.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 3C3089F7FF02F5E21612A0E8793CCC1F5A4AAE300078785DD5266310F77958DD2000:8 X-MTK: N Content-Transfer-Encoding: base64 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: T24gVGh1LCAyMDIwLTA5LTI0IGF0IDIzOjQxICswMjAwLCBUaG9tYXMgR2xlaXhuZXIgd3JvdGU6 DQo+IE9uIFRodSwgU2VwIDI0IDIwMjAgYXQgMTI6MDMsIFdhbHRlciBXdSB3cm90ZToNCj4gPiBX aGVuIGFuYWx5emUgdXNlLWFmdGVyLWZyZWUgb3IgZG91YmxlLWZyZWUgaXNzdWUsIHJlY29yZGlu ZyB0aGUgdGltZXINCj4gPiBzdGFja3MgaXMgaGVscGZ1bCB0byBwcmVzZXJ2ZSB1c2FnZSBoaXN0 b3J5IHdoaWNoIHBvdGVudGlhbGx5IGdpdmVzDQo+ID4gYSBoaW50IGFib3V0IHRoZSBhZmZlY3Rl ZCBjb2RlLg0KPiA+DQo+ID4gUmVjb3JkIHRoZSBtb3N0IHJlY2VudCB0d28gdGltZXIgaW5pdCBj YWxscyBpbiBLQVNBTiB3aGljaCBhcmUgcHJpbnRlZA0KPiA+IG9uIGZhaWx1cmUgaW4gdGhlIEtB U0FOIHJlcG9ydC4NCj4gPg0KPiA+IEZvciB0aW1lcnMgaXQgaGFzIHR1cm5lZCBvdXQgdG8gYmUg dXNlZnVsIHRvIHJlY29yZCB0aGUgc3RhY2sgdHJhY2UNCj4gPiBvZiB0aGUgdGltZXIgaW5pdCBj YWxsLg0KPiANCj4gSW4gd2hpY2ggd2F5PyBBbmQgd2hhdCBraW5kIG9mIGJ1ZyBkb2VzIGl0IGNh dGNoIHdoaWNoIGNhbm5vdCBiZSBjYXRjaGVkDQo+IGJ5IGV4aXN0aW5nIGRlYnVnIG1lY2hhbmlz bXMgYWxyZWFkeT8NCj4gDQoNCldlIG9ubHkgcHJvdmlkZSBhbm90aGVyIGRlYnVnIG1lY2hhbmlz bXMgdG8gZGVidWcgdXNlLWFmdGVyLWZyZWUgb3INCmRvdWJsZS1mcmVlLCBpdCBjYW4gYmUgZGlz cGxheWVkIHRvZ2V0aGVyIGluIEtBU0FOIHJlcG9ydCBhbmQgaGF2ZSBhDQpjaGFuY2UgdG8gZGVi dWcsIGFuZCBpdCBkb2Vzbid0IG5lZWQgdG8gZW5hYmxlIGV4aXN0aW5nIGRlYnVnIG1lY2hhbmlz bXMNCmF0IHRoZSBzYW1lIHRpbWUuIHRoZW4gaXQgaGFzIGEgY2hhbmNlIHRvIHJlc29sdmUgaXNz dWUuDQoNCj4gPiBCZWNhdXNlIGlmIHRoZSBVQUYgcm9vdCBjYXVzZSBpcyBpbiB0aW1lciBpbml0 LCB0aGVuIHVzZXIgY2FuIHNlZQ0KPiA+IEtBU0FOIHJlcG9ydCB0byBnZXQgd2hlcmUgaXQgaXMg cmVnaXN0ZXJlZCBhbmQgZmluZCBvdXQgdGhlIHJvb3QNCj4gPiBjYXVzZS4NCj4gDQo+IFdoYXQ/ IElmIHRoZSBVQUYgcm9vdCBjYXVzZSBpcyBpbiB0aW1lciBpbml0LCB0aGVuIHJlZ2lzdGVyaW5n IGl0IGFmdGVyDQo+IHVzaW5nIGl0IGluIHRoYXQgdmVyeSBzYW1lIGZ1bmN0aW9uIGlzIHByZXR0 eSBwb2ludGxlc3MuDQo+IA0KDQpTZWUgWzFdLCB0aGUgY2FsbCBzdGFjayBzaG93cyBVQUYgaGFw cGVuIGF0IGR1bW15X3RpbWVyKCksIGl0IGlzIHRoZQ0KY2FsbGJhY2sgZnVuY3Rpb24gYW5kIHNl dCBieSB0aW1lcl9zZXR1cCgpLCBpZiBLQVNBTiByZXBvcnQgc2hvd3MgdGhlDQp0aW1lciBjYWxs IHN0YWNrLCBpdCBzaG91bGQgYmUgdXNlZnVsIGZvciBwcm9ncmFtbWVyLg0KDQpbMV0NCmh0dHBz Oi8vc3l6a2FsbGVyLmFwcHNwb3QuY29tL2J1Zz9pZD0zNGU2OWI3YzhjMDE2NTY1OGNiYzk4N2Rh MGI2MWRhZGVjNjQ0YjZiDQoNCg0KPiA+IEl0IGRvbid0IG5lZWQgdG8gZW5hYmxlIERFQlVHX09C SkVDVFNfVElNRVJTLCBidXQgdGhleSBoYXZlIGEgY2hhbmNlDQo+ID4gdG8gZmluZCBvdXQgdGhl IHJvb3QgY2F1c2UuDQo+IA0KPiBUaGVyZSBpcyBhIGxvdCBvZiBoYW5kd2F2aW5nIGhvdyB1c2Vm dWwgdGhpcyBpcywgYnV0IFRCSCBJIGRvbid0IHNlZSB0aGUNCj4gdmFsdWUgYXQgYWxsLg0KPiAN Cj4gREVCVUdfT0JKRUNUU19USU1FUlMgZG9lcyBhIGxvdCBtb3JlIHRoYW4gY3Jhc2hpbmcgb24g VUFGLiBJZiBLQVNBTg0KPiBwcm92aWRlcyBhZGRpdGlvbmFsIHZhbHVlIG92ZXIgREVCVUdfT0JK RUNUU19USU1FUlMgdGhlbiBzcGVsbCBpdCBvdXQsDQo+IGJ1dCBqdXN0IHNheWluZyB0aGF0IHlv dSBkb24ndCBuZWVkIHRvIGVuYWJsZSBERUJVR19PQkpFQ1RTX1RJTUVSUyBpcw0KPiBub3QgbWFr aW5nIGFuIGFyZ3VtZW50IGZvciB0aGF0IGNoYW5nZS4NCj4gDQoNCldlIGRvbid0IHdhbnQgdG8g cmVwbGFjZSBERUJVR19PQkpFQ1RTX1RJTUVSUyB3aXRoIHRoaXMgcGF0Y2hlcywgb25seQ0KaG9w ZSB0byB1c2UgbG93IG92ZXJoZWFkKGNvbXBhcmUgd2l0aCBERUJVR19PQkpFQ1RTX1RJTUVSUykg dG8gZGVidWcNCnVzZS1hZnRlci1mcmVlL2RvdWJsZS1mcmVlIGlzc3VlLiBJZiB5b3UgaGF2ZSBz b21lIGNvbmNlcm5zLCB3ZSBjYW4gYWRkDQp0aG9zZSBtZXNzYWdlIGludG8gY29tbWl0IGxvZy4N Cg0KVGhhbmtzLg0KDQpXYWx0ZXINCg==