Bug#934304: [PATCH] tracefs: Fix potential null dereference in default_file_open()

From	Ben Hutchings <ben@decadent.org.uk>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#934304: [PATCH] tracefs: Fix potential null dereference in default_file_open()
Date	2019-08-12 02:40 +0200
Message-ID	<yu6xs-5um-5@gated-at.bofh.it> (permalink)
References	<ytatr-1mI-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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 …")
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);
 }

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Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Reinhard Karcher <reinhard.karcher@gmx.net> - 2019-08-09 12:40 +0200
  Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Reinhard Karcher <reinhard.karcher@online.de> - 2019-08-09 12:50 +0200
    Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Bernhard Übelacker <bernhardu@mailbox.org> - 2019-08-09 15:10 +0200
      Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Reinhard Karcher <reinhard.karcher@gmx.net> - 2019-08-09 15:50 +0200
        Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Bernhard Übelacker <bernhardu@mailbox.org> - 2019-08-10 16:30 +0200
          Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2 Salvatore Bonaccorso <carnil@debian.org> - 2019-08-11 12:00 +0200
  Processed: Re: Bug#934304: linux-image-5.2.0-2-amd64: powertop  aborts on version 5.2 "Debian Bug Tracking System" <owner@bugs.debian.org> - 2019-08-09 15:10 +0200
  Bug#934304: [PATCH] tracefs: Fix potential null dereference in default_file_open() Ben Hutchings <ben@decadent.org.uk> - 2019-08-12 02:40 +0200

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