[PATCH v4] signal: trace_signal_deliver when signal_group_exit

[PATCH v4] signal: trace_signal_deliver when signal_group_exit

[Zhenliang Wei]

In the fixes commit, removing SIGKILL from each thread signal mask
and executing "goto fatal" directly will skip the call to
"trace_signal_deliver". At this point, the delivery tracking of the SIGKILL
signal will be inaccurate.

Therefore, we need to add trace_signal_deliver before "goto fatal"
after executing sigdelset.

Note: SEND_SIG_NOINFO matches the fact that SIGKILL doesn't have any info.

Acked-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Fixes: cf43a757fd4944 ("signal: Restore the stop PTRACE_EVENT_EXIT")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Zhenliang Wei <weizhenliang@huawei.com>
---
 kernel/signal.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index 227ba170298e..3edf526db7c6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2441,6 +2441,8 @@ bool get_signal(struct ksignal *ksig)
 	if (signal_group_exit(signal)) {
 		ksig->info.si_signo = signr = SIGKILL;
 		sigdelset(&current->pending.signal, SIGKILL);
+		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
+			&sighand->action[signr - 1]);
 		recalc_sigpending();
 		goto fatal;
 	}
-- 
2.14.1.windows.1

Re: [PATCH v4] signal: trace_signal_deliver when signal_group_exit

[Christian Brauner]

On Wed, Apr 24, 2019 at 08:52:38PM +0800, Zhenliang Wei wrote:
> In the fixes commit, removing SIGKILL from each thread signal mask
> and executing "goto fatal" directly will skip the call to
> "trace_signal_deliver". At this point, the delivery tracking of the SIGKILL
> signal will be inaccurate.
> 
> Therefore, we need to add trace_signal_deliver before "goto fatal"
> after executing sigdelset.
> 
> Note: SEND_SIG_NOINFO matches the fact that SIGKILL doesn't have any info.
> 
> Acked-by: Christian Brauner <christian@brauner.io>

I think we're supposed to use more Reviewed-bys so feel free (or Andrew)
to change this to:

Reviewed-by: Christian Brauner <christian@brauner.io>

> Reviewed-by: Oleg Nesterov <oleg@redhat.com>
> Cc: <stable@vger.kernel.org>
> Fixes: cf43a757fd4944 ("signal: Restore the stop PTRACE_EVENT_EXIT")
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Zhenliang Wei <weizhenliang@huawei.com>
> ---
>  kernel/signal.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 227ba170298e..3edf526db7c6 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2441,6 +2441,8 @@ bool get_signal(struct ksignal *ksig)
>  	if (signal_group_exit(signal)) {
>  		ksig->info.si_signo = signr = SIGKILL;
>  		sigdelset(&current->pending.signal, SIGKILL);
> +		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
> +			&sighand->action[signr - 1]);

Hm, sorry for being the really nitpicky person here. Just for the sake
of consistency how about we do either:

+		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
+			&sighand->action[SIGKILL - 1]);

or

+		trace_signal_deliver(signr, SEND_SIG_NOINFO,
+			&sighand->action[signr - 1]);

I'm not going to argue about this though. Can just also leave it as is.

Christian

Re: [PATCH v4] signal: trace_signal_deliver when signal_group_exit

[Oleg Nesterov]

On 04/24, Christian Brauner wrote:
>
> On Wed, Apr 24, 2019 at 08:52:38PM +0800, Zhenliang Wei wrote:
>
> > Reviewed-by: Oleg Nesterov <oleg@redhat.com>

Yes, but ...

> > Reported-by: kbuild test robot <lkp@intel.com>

Hmm, really?

> > --- a/kernel/signal.c
> > +++ b/kernel/signal.c
> > @@ -2441,6 +2441,8 @@ bool get_signal(struct ksignal *ksig)
> >  	if (signal_group_exit(signal)) {
> >  		ksig->info.si_signo = signr = SIGKILL;
> >  		sigdelset(&current->pending.signal, SIGKILL);
> > +		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
> > +			&sighand->action[signr - 1]);
>
> Hm, sorry for being the really nitpicky person here. Just for the sake
> of consistency how about we do either:
>
> +		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
> +			&sighand->action[SIGKILL - 1]);
>
> or
>
> +		trace_signal_deliver(signr, SEND_SIG_NOINFO,
> +			&sighand->action[signr - 1]);

Agreed!

Oleg.