[PATCH 4.9 69/70] autofs: fix autofs_sbi() does not check super block type

Greg Kroah-Hartman
2018-09-17T22:59:23Z

From: Ian Kent <raven@themaw.net>

commit 0633da48f0793aeba27f82d30605624416723a91 upstream.

autofs_sbi() does not check the superblock magic number to verify it has
been given an autofs super block.

Backport Note: autofs4 has been renamed to autofs upstream. As a result
the upstream patch does not apply cleanly onto 4.14.y.

Link: http://lkml.kernel.org/r/153475422934.17131.7563724552005298277.stgit@pluto.themaw.net
Reported-by: <syzbot+87c3c541582e56943277@syzkaller.appspotmail.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/autofs4/autofs_i.h | 4 +++-
fs/autofs4/inode.c | 1 -
2 files changed, 3 insertions(+), 2 deletions(-)

--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -14,6 +14,7 @@
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/list.h>
+#include <linux/magic.h>

/* This is the range of ioctl() numbers we claim as ours */
#define AUTOFS_IOC_FIRST AUTOFS_IOC_READY
@@ -123,7 +124,8 @@ struct autofs_sb_info {

static inline struct autofs_sb_info *autofs4_sbi(struct super_block *sb)
{
- return (struct autofs_sb_info *)(sb->s_fs_info);
+ return sb->s_magic != AUTOFS_SUPER_MAGIC ?
+ NULL : (struct autofs_sb_info *)(sb->s_fs_info);
}

static inline struct autofs_info *autofs4_dentry_ino(struct dentry *dentry)
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -14,7 +14,6 @@
#include <linux/pagemap.h>
#include <linux/parser.h>
#include <linux/bitops.h>
-#include <linux/magic.h>
#include "autofs_i.h"
#include <linux/module.h>