I think I have the same thing going on here:

[253207.745918] BUG: unable to handle kernel NULL pointer dereference at 00000010
[253207.749013] IP: [<fb27d24b>] gss_validate+0x7b/0x1d0 [auth_rpcgss]
[253207.753994] *pde = 94fb8067 
[253207.753994] Oops: 0000 [#1] SMP 
[253207.753994] last sysfs file: /sys/devices/pci0000:00/0000:00:0b.1/usb1/1-3/1-3:1.0/host6/target6:0:0/6:0:0:0/block/sde/sde1/stat
[253207.753994] Modules linked in: xt_multiport binfmt_misc bridge stp bnep vboxnetflt vboxdrv tun des_generic cbc autofs4 video output rpcsec_gss_krb5 nfsd exportfs nfs lockd nfs_acl auth_rpcgss sunrpc nf_conntrack_ipv6 xt_hl ipt_LOG xt_limit ipt_REJECT xt_tcpudp x
[253207.842462] 
[253207.842462] Pid: 4036, comm: rpciod/1 Tainted: P           (2.6.31-14-generic #48-Ubuntu) System Product Name
[253207.842462] EIP: 0060:[<fb27d24b>] EFLAGS: 00010296 CPU: 1
[253207.842462] EIP is at gss_validate+0x7b/0x1d0 [auth_rpcgss]
[253207.842462] EAX: 00000004 EBX: 00000000 ECX: f6abde80 EDX: f28128e4
[253207.842462] ESI: 00000025 EDI: ec7b6fc4 EBP: f6abdea4 ESP: f6abde40
[253207.842462]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[253207.842462] Process rpciod/1 (pid: 4036, ti=f6abc000 task=f6a33ed0 task.ti=f6abc000)
[253207.842462] Stack:
[253207.842462]  f6abde58 c049ca59 00000001 00000001 f28128e4 e43210c0 f6abde94 00000004
[253207.842462] <0> 00000000 00000000 f6abde8c c0121270 00000000 02020202 00000004 00000004
[253207.842462] <0> 00000025 f28128e4 f6abde94 00000004 00000100 85030000 ec7b6fc4 e43210c0
[253207.842462] Call Trace:
[253207.842462]  [<c049ca59>] ? net_tx_action+0x59/0x130
[253207.842462]  [<c0121270>] ? ack_apic_level+0x60/0x230
[253207.842462]  [<fb242bf2>] ? rpcauth_checkverf+0x22/0x60 [sunrpc]
[253207.842462]  [<c014b60f>] ? irq_exit+0x2f/0x70
[253207.842462]  [<c0104f10>] ? do_IRQ+0x50/0xc0
[253207.842462]  [<fb23b2df>] ? rpc_verify_header+0x1af/0x5c0 [sunrpc]
[253207.842462]  [<c01039b0>] ? common_interrupt+0x30/0x40
[253207.842462]  [<fb23b807>] ? call_decode+0x117/0x220 [sunrpc]
[253207.842462]  [<fb33dfd0>] ? nfs4_xdr_dec_read+0x0/0x60 [nfs]
[253207.842462]  [<fb242022>] ? __rpc_execute+0x92/0x1f0 [sunrpc]
[253207.842462]  [<fb2421ab>] ? rpc_async_schedule+0xb/0x10 [sunrpc]
[253207.842462]  [<c0157a7e>] ? run_workqueue+0x6e/0x140
[253207.842462]  [<fb2421a0>] ? rpc_async_schedule+0x0/0x10 [sunrpc]
[253207.842462]  [<c0157bd8>] ? worker_thread+0x88/0xe0
[253207.842462]  [<c015c280>] ? autoremove_wake_function+0x0/0x40
[253207.842462]  [<c0157b50>] ? worker_thread+0x0/0xe0
[253207.842462]  [<c015bf8c>] ? kthread+0x7c/0x90
[253207.842462]  [<c015bf10>] ? kthread+0x0/0x90
[253207.842462]  [<c0104007>] ? kernel_thread_helper+0x7/0x10
[253207.842462] Code: 55 b4 8b 40 64 0f c8 89 45 f0 8d 45 f0 89 45 e4 8d 45 e4 c7 45 e8 04 00 00 00 e8 31 cf fc ff 8b 55 ac 8d 4d dc 89 75 dc 89 55 e0 <8b> 43 10 8d 55 b4 e8 2a 11 00 00 3d 00 00 0c 00 74 6b 85 c0 75 
[253207.842462] EIP: [<fb27d24b>] gss_validate+0x7b/0x1d0 [auth_rpcgss] SS:ESP 0068:f6abde40
[253207.842462] CR2: 0000000000000010
[253207.845072] ---[ end trace ad285e035a384c5f ]---
[253208.107509] BUG: unable to handle kernel NULL pointer dereference at 00000010
[253208.107518] IP: [<fb27d24b>] gss_validate+0x7b/0x1d0 [auth_rpcgss]
[253208.107534] *pde = aee17067 
[253208.107537] Oops: 0000 [#2] SMP 
[253208.107540] last sysfs file: /sys/devices/pci0000:00/0000:00:0b.1/usb1/1-3/1-3:1.0/host6/target6:0:0/6:0:0:0/block/sde/sde1/stat
[253208.107544] Modules linked in: xt_multiport binfmt_misc bridge stp bnep vboxnetflt vboxdrv tun des_generic cbc autofs4 video output rpcsec_gss_krb5 nfsd exportfs nfs lockd nfs_acl auth_rpcgss sunrpc nf_conntrack_ipv6 xt_hl ipt_LOG xt_limit ipt_REJECT xt_tcpudp x
[253208.107607] 
[253208.107611] Pid: 4033, comm: rpciod/0 Tainted: P      D    (2.6.31-14-generic #48-Ubuntu) System Product Name
[253208.107614] EIP: 0060:[<fb27d24b>] EFLAGS: 00010296 CPU: 0
[253208.107620] EIP is at gss_validate+0x7b/0x1d0 [auth_rpcgss]
[253208.107622] EAX: 00000004 EBX: 00000000 ECX: f64f7e80 EDX: d80a68e4
[253208.107625] ESI: 00000025 EDI: eb716c44 EBP: f64f7ea4 ESP: f64f7e40
[253208.107627]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[253208.107630] Process rpciod/0 (pid: 4033, ti=f64f6000 task=f6a34b60 task.ti=f64f6000)
[253208.107632] Stack:
[253208.107633]  c0127c38 f64f7e58 c05707da f7070000 d80a68e4 e43210c0 f64f7e94 00000004
[253208.107637] <0> 00000000 00000000 00000292 ecb2d204 00000000 c0150c2b 00000004 00000004
[253208.107641] <0> 00000025 d80a68e4 f64f7e94 00000004 2942dfc4 88030000 eb716c44 e43210c0
[253208.107646] Call Trace:
[253208.107655]  [<c0127c38>] ? default_spin_lock_flags+0x8/0x10
[253208.107660]  [<c05707da>] ? _spin_lock_irqsave+0x2a/0x40
[253208.107664]  [<c0150c2b>] ? mod_timer+0xcb/0x140
[253208.107695]  [<fb242bf2>] ? rpcauth_checkverf+0x22/0x60 [sunrpc]
[253208.107709]  [<fb23b2df>] ? rpc_verify_header+0x1af/0x5c0 [sunrpc]
[253208.107723]  [<fb23b807>] ? call_decode+0x117/0x220 [sunrpc]
[253208.107756]  [<fb33dfd0>] ? nfs4_xdr_dec_read+0x0/0x60 [nfs]
[253208.107772]  [<fb242022>] ? __rpc_execute+0x92/0x1f0 [sunrpc]
[253208.107806]  [<fb2421ab>] ? rpc_async_schedule+0xb/0x10 [sunrpc]
[253208.107811]  [<c0157a7e>] ? run_workqueue+0x6e/0x140
[253208.107836]  [<fb2421a0>] ? rpc_async_schedule+0x0/0x10 [sunrpc]
[253208.107849]  [<c0157bd8>] ? worker_thread+0x88/0xe0
[253208.107858]  [<c015c280>] ? autoremove_wake_function+0x0/0x40
[253208.107867]  [<c0157b50>] ? worker_thread+0x0/0xe0
[253208.107870]  [<c015bf8c>] ? kthread+0x7c/0x90
[253208.107873]  [<c015bf10>] ? kthread+0x0/0x90
[253208.107877]  [<c0104007>] ? kernel_thread_helper+0x7/0x10
[253208.107878] Code: 55 b4 8b 40 64 0f c8 89 45 f0 8d 45 f0 89 45 e4 8d 45 e4 c7 45 e8 04 00 00 00 e8 31 cf fc ff 8b 55 ac 8d 4d dc 89 75 dc 89 55 e0 <8b> 43 10 8d 55 b4 e8 2a 11 00 00 3d 00 00 0c 00 74 6b 85 c0 75 
[253208.107898] EIP: [<fb27d24b>] gss_validate+0x7b/0x1d0 [auth_rpcgss] SS:ESP 0068:f64f7e40
[253208.107906] CR2: 0000000000000010
[253208.107909] ---[ end trace ad285e035a384c60 ]---

Any progress on this issue?

*** Bug 14453 has been marked as a duplicate of this bug. ***

Is this only happening for NFSv4 mounted filesystems?

If so does the following patch help?

Created attachment 23508 [details]
NFSv4: Fix two unbalanced put_rpccred() issues.

Commits 29fba38b (nfs41: lease renewal) and fc01cea9 (nfs41: sequence
operation) introduce a couple of put_rpccred() calls on credentials for
which there is no corresponding get_rpccred().

(In reply to comment #3)
> Is this only happening for NFSv4 mounted filesystems?

I'm not positive as it only happened the once to me (today was the first and only occurrence) and I rolled back to a 2.6.30 kernel.

> If so does the following patch help?

I wonder if Ubuntu would be willing to add that patch as a "sauce" patch for their 9.10 RC users to test.

If it fixes the bug, I'm planning on sending it to Greg for the stable series. Ubuntu, and all other distros can pick it up from there.

I do need it tested first, though. Hopefully, at least one of you can try it out and see if it suffices to prevent the bug from reoccurring.

The patch is working fine here (NFSv4).

Does this problem affect the NFS clients only, or is there a chance for a similar problem for NFS servers?

It won't affect a server that isn't also running as a client. However it will affect anything that is running an NFSv4 client.

(In reply to comment #6)
> If it fixes the bug, I'm planning on sending it to Greg for the stable
> series.
> Ubuntu, and all other distros can pick it up from there.
> 

Works for me too (on top of 2.6.31.5), but of course the problem came up just by chance. 

Will this patch be included in 2.6.31.x?

Yes. I've already sent it to the stable kernel maintainers for consideration.

(In reply to comment #11)
> Yes. I've already sent it to the stable kernel maintainers for consideration.

How do we know when/if it gets included in the stable kernel?  Will this bug get automatically updated when/if that happens?

The patch has been merged into 2.6.31.6, so I'm closing this bug...