[PATCH] um: protect find_task_by_pid_ns() with rcu lock

[Dawei Li]

find_task_by_pid_ns() is safe if and only if it's under protection
from rcu read lock, implements the protection.

base-commit: 193cb8372424184dde28088a4230a5fed0afb0ad

Signed-off-by: Dawei Li <set_pte_at at outlook.com>
---
 arch/um/drivers/mconsole_kern.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 5026e7b9adfe..6b80e766ae80 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -683,7 +683,10 @@ void mconsole_stack(struct mc_request *req)
 		return;
 	}
 
+	rcu_read_lock();
 	to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
+	rcu_read_unlock();
+
 	if ((to == NULL) || (pid_requested == 0)) {
 		mconsole_reply(req, "Couldn't find that pid", 1, 0);
 		return;
-- 
2.25.1