Multiple Platform remote CPU load issue in Samba 1.x and2.x

J. Robert von Behren jrvb at cs.berkeley.edu
Wed Jun 14 00:38:28 GMT 2000


FWIW, I can reproduce this on my test machine (Redhat 6.0, kernel
2.2.5-15).  The following command does the trick:

     nc localhost 139 < /dev/zero

After watching smbd with gdb and strace, I found that the child smbd
that was spawned in response to the nc connection just keeps reading
zeros from the socket, and writing out error responses, ad infinitum.  A
simple fix would be to abort the connection after a certain number of
successive bad requests, or after a certain number of bad requests
within a given time period.

Best regards,

-Rob von Behren



"Allen, Michael B (RSCH)" wrote:
> 
> > -----Original Message-----
> > From: Allen, Michael B (RSCH)
> >
> >
> > but smbd seems to drop the conn.
>         [Allen, Michael B (RSCH)]
> 
>         Actually , I'm sorry this is not true. It appears to maintain the
> connection and then close when the netcat program stops but there only a few
> packets transpire on connection and then again on disconnect.
> 
>         PS:
> 
>         [root at prodlinux lib]# cat /dev/zero > /dev/null
> 
>         This runs the cpu up to 100% so I'm getting zeros
> 
>         [root at prodlinux lib]# cat /dev/zero | ./netcat localhost 139
> 
>         and this too does nothing.
> 
>         Michael B. Allen
>         http://jcifs.samba.org


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