Messages in this thread | | | From | Sergey Senozhatsky <> | Date | Sat, 16 Mar 2019 23:14:10 +0900 | Subject | Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic - not syncing: panic_on_warn set ..." |
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On (03/16/19 19:18), Tetsuo Handa wrote: > On 2019/03/16 18:11, Dmitry Vyukov wrote: > > Such reports showed up always with low frequency. For all that I > > looked at we also always had a normal non-truncated version, so I was > > never too worried. > > > > If something would write from userspace, that would show up in the > > output, or not? > > > > Perhaps syzkaller somehow manages to lower console output level? > > panic() calls console_verbose() before calling > > pr_emerg("Kernel panic - not syncing: %s\n", buf); > > line. Then, someone might have changed console_loglevel enough to > suppress printk() output.
Hmm... sysctl, may be?
> > I figured out that we should restrict it from doing > > syslog(SYSLOG_ACTION_CONSOLE_OFF). And I also restricted its access o > > /dev/console. But maybe there is something else? It _should_ not be > > able to write to random sysctl's. > > Maybe try running with "ignore_loglevel" kernel command line option added?
Right, that's something I would expect 0-day and syzkaller to do.
-ss
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