Patch "firewire: net: fix fragmented datagram_size off-by-one" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    firewire: net: fix fragmented datagram_size off-by-one

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     firewire-net-fix-fragmented-datagram_size-off-by-one.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e9300a4b7bbae83af1f7703938c94cf6dc6d308f Mon Sep 17 00:00:00 2001
From: Stefan Richter <stefanr@s5r6.in-berlin.de>
Date: Sun, 30 Oct 2016 17:32:01 +0100
Subject: firewire: net: fix fragmented datagram_size off-by-one

From: Stefan Richter <stefanr@s5r6.in-berlin.de>

commit e9300a4b7bbae83af1f7703938c94cf6dc6d308f upstream.

RFC 2734 defines the datagram_size field in fragment encapsulation
headers thus:

    datagram_size:  The encoded size of the entire IP datagram.  The
    value of datagram_size [...] SHALL be one less than the value of
    Total Length in the datagram's IP header (see STD 5, RFC 791).

Accordingly, the eth1394 driver of Linux 2.6.36 and older set and got
this field with a -/+1 offset:

    ether1394_tx() /* transmit */
        ether1394_encapsulate_prep()
            hdr->ff.dg_size = dg_size - 1;

    ether1394_data_handler() /* receive */
        if (hdr->common.lf == ETH1394_HDR_LF_FF)
            dg_size = hdr->ff.dg_size + 1;
        else
            dg_size = hdr->sf.dg_size + 1;

Likewise, I observe OS X 10.4 and Windows XP Pro SP3 to transmit 1500
byte sized datagrams in fragments with datagram_size=1499 if link
fragmentation is required.

Only firewire-net sets and gets datagram_size without this offset.  The
result is lacking interoperability of firewire-net with OS X, Windows
XP, and presumably Linux' eth1394.  (I did not test with the latter.)
For example, FTP data transfers to a Linux firewire-net box with max_rec
smaller than the 1500 bytes MTU
  - from OS X fail entirely,
  - from Win XP start out with a bunch of fragmented datagrams which
    time out, then continue with unfragmented datagrams because Win XP
    temporarily reduces the MTU to 576 bytes.

So let's fix firewire-net's datagram_size accessors.

Note that firewire-net thereby loses interoperability with unpatched
firewire-net, but only if link fragmentation is employed.  (This happens
with large broadcast datagrams, and with large datagrams on several
FireWire CardBus cards with smaller max_rec than equivalent PCI cards,
and it can be worked around by setting a small enough MTU.)

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/firewire/net.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/firewire/net.c
+++ b/drivers/firewire/net.c
@@ -73,13 +73,13 @@ struct rfc2734_header {
 
 #define fwnet_get_hdr_lf(h)		(((h)->w0 & 0xc0000000) >> 30)
 #define fwnet_get_hdr_ether_type(h)	(((h)->w0 & 0x0000ffff))
-#define fwnet_get_hdr_dg_size(h)	(((h)->w0 & 0x0fff0000) >> 16)
+#define fwnet_get_hdr_dg_size(h)	((((h)->w0 & 0x0fff0000) >> 16) + 1)
 #define fwnet_get_hdr_fg_off(h)		(((h)->w0 & 0x00000fff))
 #define fwnet_get_hdr_dgl(h)		(((h)->w1 & 0xffff0000) >> 16)
 
-#define fwnet_set_hdr_lf(lf)		((lf)  << 30)
+#define fwnet_set_hdr_lf(lf)		((lf) << 30)
 #define fwnet_set_hdr_ether_type(et)	(et)
-#define fwnet_set_hdr_dg_size(dgs)	((dgs) << 16)
+#define fwnet_set_hdr_dg_size(dgs)	(((dgs) - 1) << 16)
 #define fwnet_set_hdr_fg_off(fgo)	(fgo)
 
 #define fwnet_set_hdr_dgl(dgl)		((dgl) << 16)
@@ -622,7 +622,7 @@ static int fwnet_incoming_packet(struct
 		fg_off = fwnet_get_hdr_fg_off(&hdr);
 	}
 	datagram_label = fwnet_get_hdr_dgl(&hdr);
-	dg_size = fwnet_get_hdr_dg_size(&hdr); /* ??? + 1 */
+	dg_size = fwnet_get_hdr_dg_size(&hdr);
 
 	if (fg_off + len > dg_size)
 		return 0;


Patches currently in stable-queue which might be from stefanr@s5r6.in-berlin.de are

queue-4.4/firewire-net-fix-fragmented-datagram_size-off-by-one.patch
queue-4.4/firewire-net-guard-against-rx-buffer-overflows.patch