From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 2 Nov 2014 20:30:14 +0000 (+0800)
Subject: tun: Fix TUN_PKT_STRIP setting
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bda0832822183c326b2ee65cd7f8442532adbe36;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

tun: Fix TUN_PKT_STRIP setting

commit 2eb783c43e7cf807a45899c10ed556b6dc116625 upstream.

We set the flag TUN_PKT_STRIP if the user buffer provided is too
small to contain the entire packet plus meta-data.  However, this
has been broken ever since we added GSO meta-data.  VLAN acceleration
also has the same problem.

This patch fixes this by taking both into account when setting the
TUN_PKT_STRIP flag.

The fact that this has been broken for six years without anyone
realising means that nobody actually uses this flag.

Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
[wt: no tuntap VLAN offloading in 3.10]
Signed-off-by: Willy Tarreau <w@1wt.eu>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 582497103fe8..ea6ada39db15 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1272,12 +1272,16 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 {
 	struct tun_pi pi = { 0, skb->protocol };
 	ssize_t total = 0;
+	int vnet_hdr_sz = 0;
+
+	if (tun->flags & TUN_VNET_HDR)
+		vnet_hdr_sz = tun->vnet_hdr_sz;
 
 	if (!(tun->flags & TUN_NO_PI)) {
 		if ((len -= sizeof(pi)) < 0)
 			return -EINVAL;
 
-		if (len < skb->len) {
+		if (len < skb->len + vnet_hdr_sz) {
 			/* Packet will be striped */
 			pi.flags |= TUN_PKT_STRIP;
 		}
@@ -1287,9 +1291,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 		total += sizeof(pi);
 	}
 
-	if (tun->flags & TUN_VNET_HDR) {
+	if (vnet_hdr_sz) {
 		struct virtio_net_hdr gso = { 0 }; /* no info leak */
-		if ((len -= tun->vnet_hdr_sz) < 0)
+		if ((len -= vnet_hdr_sz) < 0)
 			return -EINVAL;
 
 		if (skb_is_gso(skb)) {
@@ -1332,7 +1336,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 		if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
 					       sizeof(gso))))
 			return -EFAULT;
-		total += tun->vnet_hdr_sz;
+		total += vnet_hdr_sz;
 	}
 
 	len = min_t(int, skb->len, len);