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Date:   Mon, 12 Aug 2019 01:28:34 +0100
From:   Ben Hutchings <ben@decadent.org.uk>
To:     jmorris@namei.org
Cc:     linux-security-module@vger.kernel.org,
        Matthew Garrett <matthewgarrett@google.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Reinhard Karcher <reinhard.karcher@gmx.net>,
        934304@bugs.debian.org
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Subject: [PATCH] tracefs: Fix potential null dereference in
 default_file_open()
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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 =E2=80=
=A6")
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;
=20
 	real_fops =3D dentry->d_fsdata;
+	if (!real_fops->open)
+		return 0;
 	return real_fops->open(inode, filp);
 }
=20

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