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.... 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 --- fs/autofs4/autofs_i.h | 4 +++- fs/autofs4/inode.c | 1 - 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h index 4737615f0eaa..ce696d6c4641 100644 --- a/fs/autofs4/autofs_i.h +++ b/fs/autofs4/autofs_i.h @@ -26,6 +26,7 @@ #include <linux/list.h> #include <linux/completion.h> #include <asm/current.h> +#include <linux/magic.h>

/* This is the range of ioctl() numbers we claim as ours */ #define AUTOFS_IOC_FIRST AUTOFS_IOC_READY @@ -124,7 +125,8 @@ 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) diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c index 09e7d68dff02..3c7e727612fa 100644 --- 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>