[PATCH 5/5] Clear si_pid for signal from ancestor ns

[Sukadev Bhattiprolu]

Since processes don't have valid pid numbers in a descendant pid namespaces,
the siginfo->si_pid field must be set to 0 when signal is sent from an
ancestor namespace.

TODO:
	- siginfo->si_pid may need to be cleared in other locations (eg:
	  __do_notify(), F_SETSIG) and will be addressed in separate patches.

	- rt_sigqueueinfo(): siginfo->si_pid value is unreliable/undefined
	  when rt_sigqueueinfo() is used to signal a process in a descendant
	  namespace

Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
---
 kernel/signal.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 8c294c1..14eb986 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -881,6 +881,8 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
 		default:
 			copy_siginfo(&q->info, info);
 			q->info.si_signo &= ~SIG_FROM_USER;
+			if (from_ancestor_ns)
+				q->info.si_pid = 0;
 			break;
 		}
 	} else if (!is_si_special(info)) {
-- 
1.5.2.5

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