[patch 34/48] tun: Fix unicast filter overflow

Greg KH
2009-02-14T01:41:42Z

[-- Attachment #1: tun-fix-unicast-filter-overflow.patch --]
[-- Type: text/plain, Size: 1622 bytes --]

2.6.28-stable review patch. If anyone has any objections, please let us know.

------------------

From: Alex Williamson <alex.williamson@hp.com>

[ Upstream commit cfbf84fcbcda98bb91ada683a8dc8e6901a83ebd ]

Tap devices can make use of a small MAC filter set via the
TUNSETTXFILTER ioctl. The filter has a set of exact matches
plus a hash for imperfect filtering of additional multicast
addresses. The current code is unbalanced, adding unicast
addresses to the multicast hash, but only checking the hash
against multicast addresses. This results in the filter
dropping unicast addresses that overflow the exact filter.
The fix is simply to disable the filter by leaving count set
to zero if we find non-multicast addresses after the exact
match table is filled.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/net/tun.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -157,10 +157,16 @@ static int update_filter(struct tap_filt

nexact = n;

- /* The rest is hashed */
+ /* Remaining multicast addresses are hashed,
+ * unicast will leave the filter disabled. */
memset(filter->mask, 0, sizeof(filter->mask));
- for (; n < uf.count; n++)
+ for (; n < uf.count; n++) {
+ if (!is_multicast_ether_addr(addr[n].u)) {
+ err = 0; /* no filter */
+ goto done;
+ }
addr_hash_set(filter->mask, addr[n].u);
+ }

/* For ALLMULTI just set the mask to all ones.
* This overrides the mask populated above. */