Messages in this thread | | | Subject | Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic - not syncing: panic_on_warn set ..." | From | Tetsuo Handa <> | Date | Sat, 16 Mar 2019 19:18:50 +0900 |
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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.
> 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?
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