[PATCH 1/6] tracefs: Fix potential null dereference in default_file_open()

From: Matthew Garrett <matthewgarrett@google.com>
To: jmorris@namei.org
Cc: linux-security-module@vger.kernel.org,
	Ben Hutchings <ben@decadent.org.uk>
Subject: [PATCH 1/6] tracefs: Fix potential null dereference in default_file_open()
Date: Tue, 13 Aug 2019 12:21:21 -0700	[thread overview]
Message-ID: <20190813192126.122370-2-matthewgarrett@google.com> (raw)
In-Reply-To: <20190813192126.122370-1-matthewgarrett@google.com>

From: Ben Hutchings <ben@decadent.org.uk>

The "open" operation in struct file_operations is optional, and
ftrace_event_id_fops does not set it.  In default_file_open(), after
all other checks have passed, return 0 if the underlying struct
file_operations does not implement open.

Fixes: 757ff7244358 ("tracefs: Restrict tracefs when the kernel is …")
References: https://bugs.debian.org/934304
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/tracefs/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 34da48036e08..761af8ce4015 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -42,6 +42,8 @@ static int default_open_file(struct inode *inode, struct file *filp)
 		return ret;
 
 	real_fops = dentry->d_fsdata;
+	if (!real_fops->open)
+		return 0;
 	return real_fops->open(inode, filp);
 }
 
-- 
2.23.0.rc1.153.gdeed80330f-goog

