On 28.07.2019 16:09, Maxime Villard wrote: > Le 27/07/2019 à 14:14, Kamil Rytarowski a écrit : >> On 25.07.2019 06:39, Masanobu SAITOH wrote: >>> Hi. >>> >>> I have two UEFI based machines. I noticed both of them didn't boot >>> with KUBSAN. After loading kernel, the video console is cleared, >>> the cursol went upper left and then hang. I couldn't see the >>> NetBSD's copyright message. >>> >>> Is this known problem? >>> >> >> I have got a local problem that I'm not successfully booting my amd64 >> desktop with enabled i915 DRM KMS Framebuffer driver. > > This could be that the KMS driver itself is generating a KUBSAN message. > So printf() gets called, it lands back in the KMS driver to print the > actual thing, which triggers again a KUBSAN message, so printf() gets > called again, and so on. It likely dies in a deadlock on whatever mutex > we take along the way. > > In Masanobu's case, it is probably that the UEFI boot path triggers a > KUBSAN message, printf() gets called, but the console hasn't yet been > initialized, so it faults and dies there. > What are the best workarounds for these problems? >> There is also a similar problem with Kernel UBSan + Kernel ASan. >> Something breaks during early boot and needs investigation. > > You should not use two kernel sanitizers at the same time. This is what we want to do now with syzbot, run one setup with kUBSan and another one with kASan. Siddharth will work on this after Monday and it was accepted by the syzbot maintainer. Hopefully kMSan will be third sanitizer.
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