From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 20 Feb 2020 14:58:42 +0000 (-0500)
Subject: Fix: statedump: check task_active_pid_ns return value for NULL
X-Git-Tag: before-upstreaming~33
X-Git-Url: http://git.lttng.org/?p=lttng-modules.git;a=commitdiff_plain;h=adcc8b5e0be84d0b8c4b414d7db5b8c54e0b0466

Fix: statedump: check task_active_pid_ns return value for NULL

The lttng-statedump checks the return value of task_active_pid_ns()
before each use within lttng_statedump_process_pid_ns(), but misses
the NULL check before dereferencing pid_ns->parent.

This race happens if a task exists in "dead" state while the statedump
iterates on that task.

Reported-by: Li Zhou <li.zhou@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/lttng-statedump-impl.c b/lttng-statedump-impl.c
index 066b9612..043bbaa1 100644
--- a/lttng-statedump-impl.c
+++ b/lttng-statedump-impl.c
@@ -426,7 +426,7 @@ void lttng_statedump_process_ns(struct lttng_session *session,
 	pid_ns = task_active_pid_ns(p);
 	do {
 		trace_lttng_statedump_process_pid_ns(session, p, pid_ns);
-		pid_ns = pid_ns->parent;
+		pid_ns = pid_ns ? pid_ns->parent : NULL;
 	} while (pid_ns);