linux-kernel - Re: [linux-cifs-client] [CIFS] still incorrect cifs

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Message-ID: <20071119064205.419e0758@tleilax.poochiereds.net>
Date:	Mon, 19 Nov 2007 06:42:05 -0500
From:	Jeff Layton <jlayton@...hat.com>
To:	Petr Tesarik <ptesarik@...e.cz>
Cc:	linux-cifs-client@...ts.samba.org,
	Steve French <smfrench@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [linux-cifs-client] [CIFS] still incorrect cifs_reconnect fix?

On Mon, 19 Nov 2007 10:30:45 +0100
Petr Tesarik <ptesarik@...e.cz> wrote:

> Hi,
> 
> while merging commits f01d5e14e764b14b6bf5512678523d009254b209 and
> 638b250766272fcaaa0f7ed2776f58f4ac701914 into SLES10, I've noticed
> that there's apparently a bug. The code currently looks like this:
> 
> 		pdu_length = 4; /* enough to get RFC1001 header */
> incomplete_rcv:
> 		length =
> 		    kernel_recvmsg(csocket, &smb_msg,
> 				&iov, 1, pdu_length, 0 /* BB other
> flags? */);
> 
> /* ... some irrelevant code left out ... */
> 
> 		} else if (length < 4) {	/* <----- HERE IS THE
> PROBLEM cFYI(1, ("less than four bytes received (%d bytes)",
> 			      length));
> 			pdu_length -= length;
> 			msleep(1);
> 			goto incomplete_rcv;
> 		}
> 
> I think we should be checking for length < pdu_length, not for length
> < 4, because if we read 2 bytes in the first run and 2 bytes in the
> second un, CIFS will still treat the second run as incomplete (and
> possibly run in an infinite loop). Am I missing something obvious?
> 

I think you're right that the logic there is wrong, but I don't see an
infinite loop happening. It looks like in this situation, that the next
call to kernel_recvmsg will be called a size of 0, which should
eventually return 0. It'll then fall into the previous condition -- do
a reconnect and then go around the big loop again.

A patch to clean that up would probably be a good thing. We likely
don't need to do a reconnect here.

--
Jeff Layton <jlayton@...hat.com>
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