udf: Detect system inodes linked into directory hierarchy

commit 85a37983ec69cc9fcd188bc37c4de15ee326355a upstream.

When UDF filesystem is corrupted, hidden system inodes can be linked
into directory hierarchy which is an avenue for further serious
corruption of the filesystem and kernel confusion as noticed by syzbot
fuzzed images. Refuse to access system inodes linked into directory
hierarchy and vice versa.

CC: stable@vger.kernel.org
Reported-by: syzbot+38695a20b8addcbc1084@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 52ffbe2b56d70027890f031af04e37f15cdde9e2..33eb3a67c31d24ae37da3e018554d8d0a0b4f348 100644 (file)
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1892,8 +1892,13 @@ struct inode *__udf_iget(struct super_block *sb, struct kernel_lb_addr *ino,
        if (!inode)
                return ERR_PTR(-ENOMEM);
 
-       if (!(inode->i_state & I_NEW))
+       if (!(inode->i_state & I_NEW)) {
+               if (UDF_I(inode)->i_hidden != hidden_inode) {
+                       iput(inode);
+                       return ERR_PTR(-EFSCORRUPTED);
+               }
                return inode;
+       }
 
        memcpy(&UDF_I(inode)->i_location, ino, sizeof(struct kernel_lb_addr));
        err = udf_read_inode(inode, hidden_inode);