Re: [PATCH] kernel/panic/kexec: fix "crash_kexec_post_notifiers" option issue in oops path

[Baoquan He]

On 02/09/15 at 12:22pm, HATAYAMA Daisuke wrote:
> Hello,
> 
> From: Baoquan He <bhe@xxxxxxxxxx>
> Subject: Re: [PATCH] kernel/panic/kexec: fix "crash_kexec_post_notifiers" option issue in oops path
> Date: Mon, 9 Feb 2015 10:40:30 +0800
> 
> > On 02/05/15 at 05:59pm, HATAYAMA Daisuke wrote:
> >> The commit f06e5153f4ae2e2f3b0300f0e260e40cb7fefd45 introduced
> >> "crash_kexec_post_notifiers" kernel boot option, which toggles
> >> wheather panic() calls crash_kexec() before or after panic_notifiers
> >> and dump kmsg.
> >> 
> >> The problem is that the commit overlooks panic_on_oops kernel boot
> >> option. If it is enabled, crash_kexec() is called directly without
> >> going through panic() in oops path.
> >> 
> >> To fix this issue, this patch adds a check to
> >> "crash_kexec_post_notifiers" in the condition of kexec_should_crash().
> >> 
> >> Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
> >> ---
> >>  include/linux/kernel.h | 3 +++
> >>  kernel/kexec.c         | 2 ++
> >>  kernel/panic.c         | 2 +-
> >>  3 files changed, 6 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> >> index 64ce58b..f47379f 100644
> >> --- a/include/linux/kernel.h
> >> +++ b/include/linux/kernel.h
> >> @@ -426,6 +426,9 @@ extern int panic_on_unrecovered_nmi;
> >>  extern int panic_on_io_nmi;
> >>  extern int panic_on_warn;
> >>  extern int sysctl_panic_on_stackoverflow;
> >> +
> >> +extern bool crash_kexec_post_notifiers;
> >> +
> >>  /*
> >>   * Only to be used by arch init code. If the user over-wrote the default
> >>   * CONFIG_PANIC_TIMEOUT, honor it.
> >> diff --git a/kernel/kexec.c b/kernel/kexec.c
> >> index 9a8a01a..0ecf252 100644
> >> --- a/kernel/kexec.c
> >> +++ b/kernel/kexec.c
> >> @@ -84,6 +84,8 @@ struct resource crashk_low_res = {
> >>  
> >>  int kexec_should_crash(struct task_struct *p)
> >>  {
> >> +	if (crash_kexec_post_notifiers)
> >> +		return 0;
> >>  	if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
> >>  		return 1;
> > 
> > What if these two conditions !p->pid || is_global_init(p) are satisfied?
> > Seems the behavious is changed.
> > 
> 
> Please further follow do_exit() path. For each condition, there are
> the corresponding panic() calls. In summary:
> 
>   oops_end
>     1) panic() for in_interrupt()
>     2) panic() for panic_on_oops
>     do_exit
>       3) panic() for !p->pid (idle task)
>       exit_notify
>         forget_original_parent
>           find_child_reaper
>             4) panic() for p->pid == 1 (init task)

Yes, all conditions have been covered.

So this patch is necessary, ACK it. Thanks

Acked-by: Baoquan He <bhe@xxxxxxxxxx>



Thanks
Baoquan

> 
> --
> Thanks.
> HATAYAMA, Daisuke
> 
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