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Subject[PATCH 4.20 05/32] vxlan: test dev->flags & IFF_UP before calling netif_rx()
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

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

[ Upstream commit 4179cb5a4c924cd233eaadd081882425bc98f44e ]

netif_rx() must be called under a strict contract.

At device dismantle phase, core networking clears IFF_UP
and flush_all_backlogs() is called after rcu grace period
to make sure no incoming packet might be in a cpu backlog
and still referencing the device.

Most drivers call netif_rx() from their interrupt handler,
and since the interrupts are disabled at device dismantle,
netif_rx() does not have to check dev->flags & IFF_UP

Virtual drivers do not have this guarantee, and must
therefore make the check themselves.

Otherwise we risk use-after-free and/or crashes.

Note this patch also fixes a small issue that came
with commit ce6502a8f957 ("vxlan: fix a use after free
in vxlan_encap_bypass"), since the dev->stats.rx_dropped
change was done on the wrong device.

Fixes: d342894c5d2f ("vxlan: virtual extensible lan")
Fixes: ce6502a8f957 ("vxlan: fix a use after free in vxlan_encap_bypass")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Petr Machata <petrm@mellanox.com>
Cc: Ido Schimmel <idosch@mellanox.com>
Cc: Roopa Prabhu <roopa@cumulusnetworks.com>
Cc: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/vxlan.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 0565f8880199d..8f022964b2d1a 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2072,7 +2072,7 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
struct pcpu_sw_netstats *tx_stats, *rx_stats;
union vxlan_addr loopback;
union vxlan_addr *remote_ip = &dst_vxlan->default_dst.remote_ip;
- struct net_device *dev = skb->dev;
+ struct net_device *dev;
int len = skb->len;

tx_stats = this_cpu_ptr(src_vxlan->dev->tstats);
@@ -2092,9 +2092,15 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
#endif
}

+ rcu_read_lock();
+ dev = skb->dev;
+ if (unlikely(!(dev->flags & IFF_UP))) {
+ kfree_skb(skb);
+ goto drop;
+ }
+
if (dst_vxlan->cfg.flags & VXLAN_F_LEARN)
- vxlan_snoop(skb->dev, &loopback, eth_hdr(skb)->h_source, 0,
- vni);
+ vxlan_snoop(dev, &loopback, eth_hdr(skb)->h_source, 0, vni);

u64_stats_update_begin(&tx_stats->syncp);
tx_stats->tx_packets++;
@@ -2107,8 +2113,10 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
rx_stats->rx_bytes += len;
u64_stats_update_end(&rx_stats->syncp);
} else {
+drop:
dev->stats.rx_dropped++;
}
+ rcu_read_unlock();
}

static int encap_bypass_if_local(struct sk_buff *skb, struct net_device *dev,
--
2.19.1


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