[PATCH 4.4 13/28] vrf: Fix use-after-free in vrf_xmit
From: Greg Kroah-Hartman
Date: Mon Mar 20 2017 - 14:38:45 EST
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx>
[ Upstream commit f7887d40e541f74402df0684a1463c0a0bb68c68 ]
KASAN detected a use-after-free:
[ 269.467067] BUG: KASAN: use-after-free in vrf_xmit+0x7f1/0x827 [vrf] at addr ffff8800350a21c0
[ 269.467067] Read of size 4 by task ssh/1879
[ 269.467067] CPU: 1 PID: 1879 Comm: ssh Not tainted 4.10.0+ #249
[ 269.467067] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[ 269.467067] Call Trace:
[ 269.467067] dump_stack+0x81/0xb6
[ 269.467067] kasan_object_err+0x21/0x78
[ 269.467067] kasan_report+0x2f7/0x450
[ 269.467067] ? vrf_xmit+0x7f1/0x827 [vrf]
[ 269.467067] ? ip_output+0xa4/0xdb
[ 269.467067] __asan_load4+0x6b/0x6d
[ 269.467067] vrf_xmit+0x7f1/0x827 [vrf]
...
Which corresponds to the skb access after xmit handling. Fix by saving
skb->len and using the saved value to update stats.
Fixes: 193125dbd8eb2 ("net: Introduce VRF device driver")
Signed-off-by: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/vrf.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -345,6 +345,7 @@ static netdev_tx_t is_ip_tx_frame(struct
static netdev_tx_t vrf_xmit(struct sk_buff *skb, struct net_device *dev)
{
+ int len = skb->len;
netdev_tx_t ret = is_ip_tx_frame(skb, dev);
if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN)) {
@@ -352,7 +353,7 @@ static netdev_tx_t vrf_xmit(struct sk_bu
u64_stats_update_begin(&dstats->syncp);
dstats->tx_pkts++;
- dstats->tx_bytes += skb->len;
+ dstats->tx_bytes += len;
u64_stats_update_end(&dstats->syncp);
} else {
this_cpu_inc(dev->dstats->tx_drps);