From: Ben Hutchings <ben@decadent.org.uk>
Date: Mon, 12 Aug 2019 00:17:32 +0000 (+0100)
Subject: tracefs: Fix potential null dereference in default_file_open()
X-Git-Tag: archive/raspbian/5.2.17-1+rpi1^2~29
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=a5091a2cc8edf3de8b86f63d2af982ce8a316ee8;p=linux.git

tracefs: Fix potential null dereference in default_file_open()

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>

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name tracefs-fix-potential-null-dereference-in-default_fi.patch
---

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 338c791c9a0..c59bd8a1998 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -41,6 +41,8 @@ static int default_open_file(struct inode *inode, struct file *filp)
 		return -EPERM;
 
 	real_fops = dentry->d_fsdata;
+	if (!real_fops->open)
+		return 0;
 	return real_fops->open(inode, filp);
 }