Bug#367125: ext2_get_inode: bad inode number

[Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de>]

"Peter Kruse" <pjodrr@gmail.com> writes:

> Hello,
> at the moment our server prints regularily like two times a minute the same
> message to kern.log:
> EXT2-fs error (device dm-5): ext2_get_inode: bad inode number: 30130240
> I checked and the inode really does not exist on the specified device (dm-5 is
> the device with minor number 5 under /dev/mapper).
> How can I find out which process is trying to access this inode?
> I thought I use strace, but attaching to nfsd is not possible, even as root.
> Regards,
>     Peter


Did you reboot the nfs server while clients had the fs mounted? Or
stoped the nfsd and run fsck or a resize? Anything that could change
the inode numbers without the clients getting any notice?

I noticed this and can reproduce it by running exportfs -u, umount,
resize2fs, mount, exportfs and then accessing some previously used
file on the nfs clients. The client (or server?) still has the old
inode numbers cached and directly access the inodes while the
resize2fs has removed it. The ext2-fs gives an error and remounts it
read-only.

I even have fears that this is caused solely by the client caching the
inode for the file. If that is the case then a malicious client could
send requests for faked inodes causing ext2-fs errors on the server
and forcing the nfs share into read-only mode. An ugly DOS attack.

MfG
        Goswin