[PATCH v2 01/22] rv: Fix out-of-bound memory access in rv_is_container_monitor()

[Nam Cao]

When rv_is_container_monitor() is called on the last monitor in
rv_monitors_list, KASAN yells:

  BUG: KASAN: global-out-of-bounds in rv_is_container_monitor+0x101/0x110
  Read of size 8 at addr ffffffff97c7c798 by task setup/221

  The buggy address belongs to the variable:
   rv_monitors_list+0x18/0x40

This is due to list_next_entry() is called on the last entry in the list.
It wraps around to the first list_head, and the first list_head is not
embedded in struct rv_monitor_def.

Fix it by checking if the monitor is last in the list.

Fixes: cb85c660fcd4 ("rv: Add option for nested monitors and include sched")
Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 kernel/trace/rv/rv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 50344aa9f7f9..544acb1f6a33 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -225,7 +225,12 @@ bool rv_is_nested_monitor(struct rv_monitor_def *mdef)
  */
 bool rv_is_container_monitor(struct rv_monitor_def *mdef)
 {
-	struct rv_monitor_def *next = list_next_entry(mdef, list);
+	struct rv_monitor_def *next;
+
+	if (list_is_last(&mdef->list, &rv_monitors_list))
+		return false;
+
+	next = list_next_entry(mdef, list);
 
 	return next->parent == mdef->monitor || !mdef->monitor->enable;
 }
-- 
2.39.5