Re: [Patch] sunrpc: NULL utsname dereference on NFS umount during namespace cleanup

[Trond Myklebust <trond.myklebust@primarydata.com>]

On Mon, Feb 2, 2015 at 12:41 PM, Nix <nix@esperi.org.uk> wrote:
> On 31 Jan 2015, nix@esperi.org.uk told this:
>> I'll let it run overnight and give it a reboot in the morning.
>
> Alas, my latest reboot hit:
>
> [  215.245158] BUG: unable to handle kernel NULL pointer dereference at 00000004
> [  215.251602] IP: [<c034fb8c>] rpc_new_client+0x13b/0x1f2
> [  215.251602] *pde = 00000000
> [  215.251602] Oops: 0000 [#1]
> [  215.251602] CPU: 0 PID: 398 Comm: bash Not tainted 3.18.5+ #1
> [  215.251602] task: de1fcfc0 ti: de1fa000 task.ti: de1fa000
> [  215.251602] EIP: 0060:[<c034fb8c>] EFLAGS: 00010246 CPU: 0
> [  215.251602] EIP is at rpc_new_client+0x13b/0x1f2
> [  215.251602] EAX: 00000000 EBX: df70f000 ECX: 0000bae0 EDX: 00000005
> [  215.251602] ESI: 00000000 EDI: df6cc000 EBP: 00000007 ESP: de1fbcac
> [  215.251602]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
> [  215.251602] CR0: 8005003b CR2: 00000004 CR3: 1f645000 CR4: 00000090
> [  215.251602] Stack:
> [  215.251602]  000000d0 df6cc000 de1fbd4c 00000000 de1fbd4c de1fbd4c de1fbd10 de1fbf8c
> [  215.251602]  c0350196 de1fbd4c de2056d0 de1fbd10 c0350300 c0262e32 c0263841 df528000
> [  215.251602]  a2e0b542 00000006 c044b178 00000000 de1fbddc 00000010 de2056d0 00000000
> [  215.251602] Call Trace:
> [  215.251602]  [<c0350196>] ? rpc_create_xprt+0xc/0x74
> [  215.251602]  [<c0350300>] ? rpc_create+0x102/0x10f
> [  215.251602]  [<c0262e32>] ? ata_sff_check_status+0x8/0x9
> [  215.251602]  [<c0263841>] ? ata_dev_select.constprop.20+0x83/0x95
> [  215.251602]  [<c019ec6a>] ? __block_commit_write.isra.25+0x56/0x7f
> [  215.251602]  [<c0359f04>] ? rpcb_create+0x6e/0x7c
> [  215.251602]  [<c035a677>] ? rpcb_getport_async+0x124/0x25a
> [  215.251602]  [<c0133bdf>] ? update_curr+0x81/0xb3
> [  215.251602]  [<c0133e97>] ? check_preempt_wakeup+0xf0/0x134
> [  215.251602]  [<c013110f>] ? check_preempt_curr+0x21/0x59
> [  215.251602]  [<c0355294>] ? rpcauth_lookupcred+0x3f/0x47
> [  215.251602]  [<c017ebb6>] ? __kmalloc+0xa3/0xc4
> [  215.251602]  [<c0354c09>] ? rpc_malloc+0x39/0x48
> [  215.251602]  [<c034ef05>] ? call_bind+0x2d/0x2e
> [  215.251602]  [<c0354a71>] ? __rpc_execute+0x5c/0x187
> [  215.251602]  [<c03500be>] ? rpc_run_task+0x55/0x5a
> [  215.251602]  [<c035012c>] ? rpc_call_sync+0x69/0x81
> [  215.251602]  [<c01e219e>] ? nsm_mon_unmon+0x8c/0xa0
> [  215.251602]  [<c01e23c5>] ? nsm_unmonitor+0x5f/0xd3
> [  215.251602]  [<c016b3cc>] ? bdi_unregister+0xf2/0x100
> [  215.251602]  [<c01df4cc>] ? nlm_destroy_host_locked+0x4f/0x7c
> [  215.251602]  [<c01df703>] ? nlmclnt_release_host+0xd8/0xe5
> [  215.251602]  [<c01dddd5>] ? nlmclnt_done+0xc/0x14
> [  215.251602]  [<c01ce621>] ? nfs_free_server+0x16/0x72
> [  215.251602]  [<c01837a4>] ? deactivate_locked_super+0x26/0x37
> [  215.251602]  [<c019493e>] ? cleanup_mnt+0x40/0x59
> [  215.251602]  [<c012e185>] ? task_work_run+0x4f/0x5f
> [  215.251602]  [<c0121373>] ? do_exit+0x264/0x670
> [  215.251602]  [<c0127a2b>] ? __set_current_blocked+0xd/0xf
> [  215.251602]  [<c0127b26>] ? sigprocmask+0x77/0x87
> [  215.251602]  [<c012e097>] ? __task_pid_nr_ns+0x3a/0x41
> [  215.251602]  [<c012e019>] ? find_vpid+0xd/0x17
> [  215.251602]  [<c01217cc>] ? do_group_exit+0x2b/0x5d
> [  215.251602]  [<c012180d>] ? SyS_exit_group+0xf/0xf
> [  215.251602]  [<c03679b6>] ? syscall_call+0x7/0x7
> [  215.251602] Code: 89 43 40 8b 44 24 04 89 43 18 8d 43 78 8b 53 40 89 43 3c 8b 12 e8 32 ac 00 00 c7 03 01 00 00 00 a1 dc f0 42 c0 8b 80 00 03 00 00 <8b> 70 04 83 c6 45 89 f0 e8 ab d1 eb ff 83 f8 20 7f 05 89 43 44
> [  215.251602] EIP: [<c034fb8c>] rpc_new_client+0x13b/0x1f2 SS:ESP 0068:de1fbcac
> [  215.251602] CR2: 0000000000000004
> [  215.251602] ---[ end trace 4b9e971f6b3f2dc8 ]---
> [  215.251602] Kernel panic - not syncing: Fatal exception
> [  215.251602] Kernel Offset: 0x0 from 0xc0100000 (relocation range: 0xc0000000-0xe07fffff)
> [  215.251602] Rebooting in 5 seconds..
>
> so clearly the bug is still there; also the connection I thought might
> exist with the "xprt_adjust_timeout: rq_timeout = 0!" was illusory: that
> message hadn't recurred since before the last reboot but one, but the
> crash happened anyway.
>

Hmm... I'm at a loss to see how rpcb_create can ever call
rpc_new_client() with a null value for the nodename with that patch
applied. Are you 100% sure that the above Oops came from a patched
kernel? That IP address of "rpc_new_client+0x13b/0x1f2" looks
identical to the one in your original posting.

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com