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xen-netback: don't disconnect frontend when seeing oversize packet

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Some frontend drivers are sending packets > 64 KiB in length. This length
overflows the length field in the first slot making the following slots have
an invalid length.

Turn this error back into a non-fatal error by dropping the packet. To avoid
having the following slots having fatal errors, consume all slots in the
packet.

This does not reopen the security hole in XSA-39 as if the packet as an
invalid number of slots it will still hit fatal error case.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Liu 2013-04-22 02:20:43 +00:00 committed by David S. Miller
parent 2810e5b9a7
commit 03393fd5cc
1 changed files with 16 additions and 6 deletions
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22
drivers/net/xen-netback/netback.c
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@ -975,12 +975,22 @@ static int netbk_count_requests(struct xenvif *vif,
memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
sizeof(*txp));
if (txp->size > first->size) {
netdev_err(vif->dev,
"Invalid tx request, slot size %u > remaining size %u\n",
txp->size, first->size);
netbk_fatal_tx_err(vif);
return -EIO;
/* If the guest submitted a frame >= 64 KiB then
* first->size overflowed and following slots will
* appear to be larger than the frame.
*
* This cannot be fatal error as there are buggy
* frontends that do this.
*
* Consume all slots and drop the packet.
*/
if (!drop_err && txp->size > first->size) {
if (net_ratelimit())
netdev_dbg(vif->dev,
"Invalid tx request, slot size %u > remaining size %u\n",
txp->size, first->size);
drop_err = -EIO;
}
first->size -= txp->size;