fs: Avoid userspace mounting anon_inodefs filesystem

anon_inodefs filesystem is a kernel internal filesystem userspace
shouldn't mess with. Remove registration of it so userspace cannot
even try to mount it (which would fail anyway because the filesystem is
MS_NOUSER).

This fixes an oops triggered by trinity when it tried mounting
anon_inodefs which overwrote anon_inode_inode pointer while other CPU
has been in anon_inode_getfile() between ihold() and d_instantiate().
Thus effectively creating dentry pointing to an inode without holding a
reference to it.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 24084732b1d0b264b5c3262796f1ec3dd5fc505f..4b4543b8b894124a0eb28496e9235d61328b3a8c 100644 (file)
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -177,9 +177,6 @@ static int __init anon_inode_init(void)
 {
        int error;
 
-       error = register_filesystem(&anon_inode_fs_type);
-       if (error)
-               goto err_exit;
        anon_inode_mnt = kern_mount(&anon_inode_fs_type);
        if (IS_ERR(anon_inode_mnt)) {
                error = PTR_ERR(anon_inode_mnt);