Re: linux-next NFSD: NULL pointer dereference at nfsd_svc()

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Aug 04, 2010 at 09:13:48AM +0900, Tetsuo Handa wrote:
> J. Bruce Fields wrote:
> > How about this?
> 
> After reverting commit 86d0cc3b91315c475c1c38ee7a06b5ebe5c01755 and applying
> commit 3deb279d6e5625407919a875db3a2461199566b3, I get below NULL pointer
> dereference problem when doing "mount 127.0.0.1:/usr/src/ /mnt/".

OK, I'm not seeing the explanation yet.....

> 
> [   96.398495] BUG: unable to handle kernel NULL pointer dereference at 00000010
> [   96.400348] IP: [<c1356dd4>] svc_process_common+0x2c4/0x5c0

Maybe figuring out exactly hwere that is would help work out what's
going on.  Doing

	make net/sunrpc/svc.lst

then looking for c1356dd4 (or just mailing me svc.lst) could help.


> [   96.401606] *pde = 00000000 
> [   96.401606] Oops: 0002 [#1] SMP DEBUG_PAGEALLOC
> [   96.401606] last sysfs file: /sys/devices/pci0000:00/0000:00:10.0/host0/target0:0:1/0:0:1:0/type
> [   96.401606] Modules linked in: nfs ipv6 pcnet32
> [   96.401606] 
> [   96.401606] Pid: 2623, comm: nfsd Tainted: G        W   2.6.35-next-20100802 #4 440BX Desktop Reference Platform/VMware Virtual Platform
> [   96.401606] EIP: 0060:[<c1356dd4>] EFLAGS: 00010246 CPU: 1
> [   96.401606] EIP is at svc_process_common+0x2c4/0x5c0
> [   96.401606] EAX: 00000000 EBX: dfb8b0c8 ECX: 00000001 EDX: 00000004
> [   96.401606] ESI: dfb8b0f0 EDI: 00000010 EBP: dcac4f40 ESP: dcac4ef0
> [   96.401606]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
> [   96.401606] Process nfsd (pid: 2623, ti=dcac4000 task=dc85a7b0 task.ti=dcac4000)
> [   96.401606] Stack:
> [   96.401606]  dc85a7b0 00000002 00000000 dc85ac5c dc85a7b0 dcac4f28 00000004 00000000
> [   96.401606] <0> 00000002 000186a3 dcb6c008 dcb6c014 dc805f30 c154ca20 c154cca8 dfb8b000
> [   96.401606] <0> 01000000 8c4194fd dfb8b000 dfb8b0c8 dcac4f68 c13571cf dcac4f68 c105d087
> [   96.401606] Call Trace:
> [   96.401606]  [<c13571cf>] ? svc_process+0xff/0x110
> [   96.401606]  [<c105d087>] ? __validate_process_creds+0x47/0xd0
> [   96.401606]  [<c1145739>] ? nfsd+0xc9/0x160
> [   96.401606]  [<c1035f86>] ? complete+0x46/0x60
> [   96.401606]  [<c1055d05>] ? kthread+0x75/0x80
> [   96.401606]  [<c1145670>] ? nfsd+0x0/0x160
> [   96.401606]  [<c1055c90>] ? kthread+0x0/0x80
> [   96.401606]  [<c100317a>] ? kernel_thread_helper+0x6/0x1c
> [   96.401606] Code: 4d dc c7 01 00 00 00 00 8b 55 e4 83 46 04 04 8b 42 10 ff 42 18 8b 4d ec 8b b9 6c 0d 00 00 89 45 c8 89 c1 c1 e9 02 31 c0 8b 55 c8 <f3> ab f6 c2 02 74 02 66 ab f6 c2 01 74 01 aa 8b 45 e4 8b 4d ec 
> [   96.401606] EIP: [<c1356dd4>] svc_process_common+0x2c4/0x5c0 SS:ESP 0068:dcac4ef0
> [   96.401606] CR2: 0000000000000010
> [   96.527321] ---[ end trace 0de1e1ad73b15980 ]---
> 
> > (By the way, are you using something other than the standard
> > /etc/init.d/nfs-kernel-server to start/stop the server?  Or have you
> > customized your installation in any way?  Just curious, as the bugs
> > you're finding are good, but I'd expect different symptoms from the
> > default setup.)
> I'm using standard /etc/init.d/nfs-kernel-server script installed by Debian
> Sarge and using it without modification.

OK, I wonder if Sarge didn't yet mount the nfsd filesystem on
/proc/fs/nfsd.

--b.

> 
> # ls -l /etc/init.d/nfs-*
> -rwxr-xr-x  1 root root 1984 Jan  5  2005 /etc/init.d/nfs-common
> -rwxr-xr-x  1 root root 2356 Aug  4  2003 /etc/init.d/nfs-kernel-server
> -rwxr-xr-x  1 root root 1241 Jan 30  2006 /etc/init.d/nfs-user-server
> 
> Regards.