linux-kernel - [for-linus][PATCH 7/7] rv: Fix out-of-bound memory access in rv_is_container

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Message-ID: <20250412210511.320072168@goodmis.org>
Date: Sat, 12 Apr 2025 17:04:53 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 stable@...r.kernel.org,
 Gabriele Monaco <gmonaco@...hat.com>,
 Nam Cao <namcao@...utronix.de>
Subject: [for-linus][PATCH 7/7] rv: Fix out-of-bound memory access in rv_is_container_monitor()

From: Nam Cao <namcao@...utronix.de>

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.

Cc: stable@...r.kernel.org
Cc: Gabriele Monaco <gmonaco@...hat.com>
Fixes: cb85c660fcd4 ("rv: Add option for nested monitors and include sched")
Link: https://lore.kernel.org/e85b5eeb7228bfc23b8d7d4ab5411472c54ae91b.1744355018.git.namcao@linutronix.de
Signed-off-by: Nam Cao <namcao@...utronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 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 968c5c3b0246..e4077500a91d 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;
 }
-- 
2.47.2