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([2001:b07:6468:f312:541f:a977:4b60:6802]) by smtp.gmail.com with ESMTPSA id e18sm11632611wrr.95.2019.12.05.03.29.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Dec 2019 03:29:22 -0800 (PST) Subject: Re: KASAN: slab-out-of-bounds Read in fbcon_get_font To: Dmitry Vyukov Cc: syzbot , Andrey Ryabinin , Bartlomiej Zolnierkiewicz , Daniel Thompson , Daniel Vetter , DRI , ghalat@redhat.com, Gleb Natapov , gwshan@linux.vnet.ibm.com, "H. Peter Anvin" , James Morris , kasan-dev , KVM list , Linux Fbdev development list , LKML , linux-security-module , Maarten Lankhorst , Ingo Molnar , Michael Ellerman , Tetsuo Handa , Russell Currey , Sam Ravnborg , "Serge E. Hallyn" , stewart@linux.vnet.ibm.com, syzkaller-bugs , Kentaro Takeda , Thomas Gleixner , the arch/x86 maintainers References: <0000000000003e640e0598e7abc3@google.com> <41c082f5-5d22-d398-3bdd-3f4bf69d7ea3@redhat.com> From: Paolo Bonzini Message-ID: Date: Thu, 5 Dec 2019 12:29:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-MC-Unique: EcMLIqeQMROfIgiO1mpN_g-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 05/12/19 12:27, Dmitry Vyukov wrote: > Oh, you mean the final bisection crash. Indeed it contains a kvm frame > and it turns out to be a bug in syzkaller code that indeed > misattributed it to kvm instead of netfilter. > Should be fixed now, you may read the commit message for details: > https://github.com/google/syzkaller/commit/4fb74474cf0af2126be3a8989d770c3947ae9478 > > Overall this "making sense out of kernel output" task is the ultimate > insanity, you may skim through this file to get a taste of amount of > hardcoding and special corner cases that need to be handled: > https://github.com/google/syzkaller/blob/master/pkg/report/linux.go > And this is never done, such "exception from exception corner case" > things pop up every week. There is always something to shuffle and > tune. It only keeps functioning due to 500+ test cases for all > possible insane kernel outputs: > https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/report > https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/guilty > > So thanks for persisting and questioning! We are getting better with > each new test. Thanks to you! I "complain" because I know you're so responsive. :) Paolo