Comment 42 for bug 683938

Because we run a modified kernel, it would be inconvenient to need to
install a vanilla system in order to verify the fix there. Etienne has/had a
vanilla setup reproducing the bug. I can confirm that the patch successfully
solves the problem for our kernel.

Thomas

On Thu, Jan 13, 2011 at 8:34 AM, Steve Conklin <email address hidden>wrote:

> This bug is awaiting verification that the kernel in -proposed solves
> the problem. Please test the kernel and update this bug with the
> results. If the problem is solved, change the tag 'verification-needed'
> to 'verification-done'.
>
> If verification is not done by one week from today, this fix will be
> dropped from the source code, and this bug will be closed.
>
> See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
> to enable and use -proposed. Thank you!
>
> --
> You received this bug notification because you are a direct subscriber
> of the bug.
> https://bugs.launchpad.net/bugs/683938
>
> Title:
> kernel crash on symlink chased from NFS to failing automount
>
> Status in The Linux Kernel:
> Unknown
> Status in “linux” package in Ubuntu:
> Fix Released
> Status in “linux” source package in Lucid:
> Fix Committed
> Status in “linux” source package in Maverick:
> Fix Committed
> Status in “linux” source package in Natty:
> Fix Released
>
> Bug description:
> SRU justification:
>
> Impact: When trying to mount an export where server and client have no
> common authentication method, the client will abort the mount by
> sending an advisory unmount message to the server. A bug in the RPC
> client setup causes the sunrpc code to access memory outside an
> allocated array, which will sooner or later cause the kernel to crash.
>
> Fix: Patch from upstream (about to be submitted and targeted for
> stable too) changes the setup to use the actual array size instead of
> a manually entered number.
>
> Testcase:
>
> Server exports a mount with an authentication method the client does not
> support, eg.:
> [/etc/exports] /srv/foo *(rw,sec=krb5)
>
> Client tries to mount this directory with no special authentication
> method:
> while true; do mount <server>:/srv/foo /mnt; sync; sleep 1; done
>
> ---
>
> Create an automount indirect map entry to a nfs server that will deny the
> mount with a permission denied error.
> Create a symlink on some mounted NFS partition pointing at the name of
> that automount indirect map entry.
> Chase the symlink with ls, etc.
> Notice that the automounter tries and fails to mount the partition.
> (visible with automount -d -f, say)
>
> In a few minutes, depending on system activity, the kernel will crash
> with the symptoms of a memory corruption error.
>
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>