linux-kernel - [PATCH 3.10 222/250] tun: Fix TUN_PKT

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Date:   Thu,  8 Jun 2017 01:00:08 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 222/250] tun: Fix TUN_PKT_STRIP setting

From: Herbert Xu <herbert@...dor.apana.org.au>

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@...dor.apana.org.au>
Signed-off-by: David S. Miller <davem@...emloft.net>
[wt: no tuntap VLAN offloading in 3.10]
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/net/tun.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 5824971..ea6ada3 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);
-- 
2.8.0.rc2.1.gbe9624a