Subject: [PATCH 01/21] ipv4: remove BUG_ON() from fib_compute_spec_dst

From: Lorenzo Bianconi <[email-masked]>
Date: Fri, 27 Jul 2018 18:15:46 +0200

[ Upstream commit 9fc12023d6f51551d6ca9ed7e02ecc19d79caf17 ]

Remove BUG_ON() from fib_compute_spec_dst routine and check
in_dev pointer during flowi4 data structure initialization.
fib_compute_spec_dst routine can be run concurrently with device removal
where ip_ptr net_device pointer is set to NULL. This can happen
if userspace enables pkt info on UDP rx socket and the device
is removed while traffic is flowing

Fixes: 35ebf65e851c ("ipv4: Create and use fib_compute_spec_dst() helper")
Signed-off-by: Lorenzo Bianconi <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv4/fib_frontend.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 511d6748ea5f..6901349f07d7 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -292,19 +292,19 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
 		return ip_hdr(skb)->daddr;
 
 	in_dev = __in_dev_get_rcu(dev);
-	BUG_ON(!in_dev);
 
 	net = dev_net(dev);
 
 	scope = RT_SCOPE_UNIVERSE;
 	if (!ipv4_is_zeronet(ip_hdr(skb)->saddr)) {
+		bool vmark = in_dev && IN_DEV_SRC_VMARK(in_dev);
 		struct flowi4 fl4 = {
 			.flowi4_iif = LOOPBACK_IFINDEX,
 			.flowi4_oif = l3mdev_master_ifindex_rcu(dev),
 			.daddr = ip_hdr(skb)->saddr,
 			.flowi4_tos = RT_TOS(ip_hdr(skb)->tos),
 			.flowi4_scope = scope,
-			.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0,
+			.flowi4_mark = vmark ? skb->mark : 0,
 		};
 		if (!fib_lookup(net, &fl4, &res, 0))
 			return FIB_RES_PREFSRC(net, res);
-- 
2.17.1