linux-kernel - [for-next][PATCH 7/7] eventfs: Fix a possible null pointer dereference in eventfs_find

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Date: Tue, 14 May 2024 12:14:45 -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,
 Hao Ge <gehao@...inos.cn>
Subject: [for-next][PATCH 7/7] eventfs: Fix a possible null pointer dereference in
 eventfs_find_events()

From: Hao Ge <gehao@...inos.cn>

In function eventfs_find_events,there is a potential null pointer
that may be caused by calling update_events_attr which will perform
some operations on the members of the ei struct when ei is NULL.

Hence,When ei->is_freed is set,return NULL directly.

Link: https://lore.kernel.org/linux-trace-kernel/20240513053338.63017-1-hao.ge@linux.dev

Cc: stable@...r.kernel.org
Fixes: 8186fff7ab64 ("tracefs/eventfs: Use root and instance inodes as default ownership")
Signed-off-by: Hao Ge <gehao@...inos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 fs/tracefs/event_inode.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index a878cea70f4c..0256afdd4acf 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -345,10 +345,9 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
 		 * If the ei is being freed, the ownership of the children
 		 * doesn't matter.
 		 */
-		if (ei->is_freed) {
-			ei = NULL;
-			break;
-		}
+		if (ei->is_freed)
+			return NULL;
+
 		// Walk upwards until you find the events inode
 	} while (!ei->is_events);
 
-- 
2.43.0