NFSv3/TCP in 14.10 major issues and kernel NULL pointer dereference

[David]

Upgraded a NFS client to 14.10. Server is running FreeBSD 10.0, no changes on server from when client was running 14.04. Client is using NFSv3 over TCP.

Client hosts virtual machines - first virtual machine starts ok, second virtual machine starts but machine needs to fsck and reports timeouts, left overnight still cannot complete fsck. A simple "ls" of the NFS share hangs.

3.16.0-22-generic kernel kern.log generates warning and the Oops with null pointer dereference (see attached).

Tried mainline 3.16.6-031606-generic with same result (see attached). Same behaviour, fsck never finishes and ls hangs.

Tried mainline 3.14.22-031422-generic and problem is gone, fsck finishes in several seconds, no problems with ls, machine and VMs running normally since.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1384659

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.18 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.18-rc1-utopic/

[David (mardraum)]

Installed a new host to test with and replicated the bug on it with 3.16.0-22-generic by installing a new VM - the Oops occurred during the grub2 install.

Installed 3.18.0-031800rc1-generic but the system will not even allow a VM to start, kworker and modprobe timeouts in kern.log.

[David (mardraum)]

This commit looks like it potentially fixes this issue:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3caa0c6ed754d91b15266abf222498edbef982bd

[David (mardraum)]

Tried 3.16.7 mainline and can no longer reproduce the issue. The commit "NFS: Fix an uninitialised pointer Oops in the writeback error path" appears to be the fix.

[Tim Gardner (timg-tpi)]

The next release of the Utopic kernel (3.16.0-25.33) will contain this patch.