netdev - [PATCH] packet: Allow packets with only a header (but no payload)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1448067012-15090-1-git-send-email-martin.blumenstingl@googlemail.com>
Date:	Sat, 21 Nov 2015 01:50:12 +0100
From:	Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:	netdev@...r.kernel.org
Cc:	willemb@...gle.com, edumazet@...gle.com, dborkman@...hat.com,
	davem@...emloft.net, mostrows@...thlink.net, nbd@...nwrt.org,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH] packet: Allow packets with only a header (but no payload)

9c70776 added validation for the packet size in packet_snd. This change
enforced that every packet needs a header with at least hard_header_len
bytes  and at least one byte payload.

This fixes PPPoE connections which do not have a "Service" or
"Host-Uniq" configured (which is violating the spec, but is still
widely used in real-world setups). Those are currently failing with the
following message: "pppd: packet size is too short (24 <= 24)"

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
v2: Simply change the existing logic in ll_header_truncated instead of
    splitting it and having multiple checks.

 include/linux/netdevice.h | 3 ++-
 net/packet/af_packet.c    | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 67bfac1..1f42cb7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1398,7 +1398,8 @@ enum netdev_priv_flags {
  *	@dma:		DMA channel
  *	@mtu:		Interface MTU value
  *	@type:		Interface hardware type
- *	@hard_header_len: Hardware header length
+ *	@hard_header_len: Hardware header length, which means that this is the
+ * 				minimum size of a packet.
  *
  *	@needed_headroom: Extra headroom the hardware may need, but not in all
  *			  cases can this be guaranteed
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1cf928f..992396a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2329,8 +2329,8 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
 static bool ll_header_truncated(const struct net_device *dev, int len)
 {
 	/* net device doesn't like empty head */
-	if (unlikely(len <= dev->hard_header_len)) {
-		net_warn_ratelimited("%s: packet size is too short (%d <= %d)\n",
+	if (unlikely(len < dev->hard_header_len)) {
+		net_warn_ratelimited("%s: packet size is too short (%d < %d)\n",
 				     current->comm, len, dev->hard_header_len);
 		return true;
 	}
-- 
2.6.2

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html