Re: [2.4.21]: nbd ksymoops-report

From: Paul Clements (kernel@steeleye.com)
Date: Thu Aug 07 2003 - 11:53:27 EST


On Thu, 7 Aug 2003, Bernd Schubert wrote:

> every time when nbd-client disconnects a nbd-device the decoded oops
> from below will happen.
> This only happens after we upgraded from 2.4.20 to 2.4.21,
> so I guess the backported update from 2.5.50 causes this.

Yes, it's definitely related to this...

> Aug 6 17:24:31 goedel kernel: Process nbd-client (pid: 650, stackpage=d61a5000)

Are you using the v2.0 nbd-client from nbd.sf.net?

> Code; d89e2be7 <[nbd]nbd_ioctl+353/480>
> 00000000 <_EIP>:
> Code; d89e2be7 <[nbd]nbd_ioctl+353/480> <=====
> 0: 8b 50 08 mov 0x8(%eax),%edx <=====
> Code; d89e2bea <[nbd]nbd_ioctl+356/480>
> 3: 6a 03 push $0x3
> Code; d89e2bec <[nbd]nbd_ioctl+358/480>
> 5: 50 push %eax
> Code; d89e2bed <[nbd]nbd_ioctl+359/480>
> 6: 8b 42 28 mov 0x28(%edx),%eax
> Code; d89e2bf0 <[nbd]nbd_ioctl+35c/480>
> 9: ff d0 call *%eax

This corresponds to the following source:

lo->sock->ops->shutdown(lo->sock, SEND_SHUTDOWN|RCV_SHUTDOWN);

Somehow, lo->sock is NULL here. The only way I see that this could
happen is if NBD_CLEAR_SOCK got called out of order (or you're
using some non-standard nbd-client).

I guess it would be best to protect the NULLing of lo->sock
in NBD_CLEAR_SOCK just in case, anyway.

Would you be willing to test a patch against 2.4.21?

--
Paul

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