From ed7cbbce544856b20e5811de373cf92e92499771 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Thu, 12 May 2016 16:23:44 -0700 Subject: [PATCH] udp: Resolve NULL pointer dereference over flow-based vxlan device While testing an OpenStack configuration using VXLANs I saw the following call trace: RIP: 0010:[] udp4_lib_lookup_skb+0x49/0x80 RSP: 0018:ffff88103867bc50 EFLAGS: 00010286 RAX: ffff88103269bf00 RBX: ffff88103269bf00 RCX: 00000000ffffffff RDX: 0000000000004300 RSI: 0000000000000000 RDI: ffff880f2932e780 RBP: ffff88103867bc60 R08: 0000000000000000 R09: 000000009001a8c0 R10: 0000000000004400 R11: ffffffff81333a58 R12: ffff880f2932e794 R13: 0000000000000014 R14: 0000000000000014 R15: ffffe8efbfd89ca0 FS: 0000000000000000(0000) GS:ffff88103fd80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000488 CR3: 0000000001c06000 CR4: 00000000001426e0 Stack: ffffffff81576515 ffffffff815733c0 ffff88103867bc98 ffffffff815fcc17 ffff88103269bf00 ffffe8efbfd89ca0 0000000000000014 0000000000000080 ffffe8efbfd89ca0 ffff88103867bcc8 ffffffff815fcf8b ffff880f2932e794 Call Trace: [] ? skb_checksum+0x35/0x50 [] ? skb_push+0x40/0x40 [] udp_gro_receive+0x57/0x130 [] udp4_gro_receive+0x10b/0x2c0 [] inet_gro_receive+0x1d3/0x270 [] dev_gro_receive+0x269/0x3b0 [] napi_gro_receive+0x38/0x120 [] gro_cell_poll+0x57/0x80 [vxlan] [] net_rx_action+0x160/0x380 [] __do_softirq+0xd7/0x2c5 [] run_ksoftirqd+0x29/0x50 [] smpboot_thread_fn+0x10f/0x160 [] ? sort_range+0x30/0x30 [] kthread+0xd8/0xf0 [] ret_from_fork+0x22/0x40 [] ? kthread_park+0x60/0x60 The following trace is seen when receiving a DHCP request over a flow-based VXLAN tunnel. I believe this is caused by the metadata dst having a NULL dev value and as a result dev_net(dev) is causing a NULL pointer dereference. To resolve this I am replacing the check for skb_dst(skb)->dev with just skb->dev. This makes sense as the callers of this function are usually in the receive path and as such skb->dev should always be populated. In addition other functions in the area where these are called are already using dev_net(skb->dev) to determine the namespace the UDP packet belongs in. Fixes: 63058308cd55 ("udp: Add udp6_lib_lookup_skb and udp4_lib_lookup_skb") Signed-off-by: Alexander Duyck Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/udp.c | 10 ++-------- net/ipv6/udp.c | 8 +++----- 2 files changed, 5 insertions(+), 13 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index f67f52ba4809..2e3ebfe5549e 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -604,7 +604,7 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb, { const struct iphdr *iph = ip_hdr(skb); - return __udp4_lib_lookup(dev_net(skb_dst(skb)->dev), iph->saddr, sport, + return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport, iph->daddr, dport, inet_iif(skb), udptable, skb); } @@ -612,13 +612,7 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb, struct sock *udp4_lib_lookup_skb(struct sk_buff *skb, __be16 sport, __be16 dport) { - const struct iphdr *iph = ip_hdr(skb); - const struct net_device *dev = - skb_dst(skb) ? skb_dst(skb)->dev : skb->dev; - - return __udp4_lib_lookup(dev_net(dev), iph->saddr, sport, - iph->daddr, dport, inet_iif(skb), - &udp_table, skb); + return __udp4_lib_lookup_skb(skb, sport, dport, &udp_table); } EXPORT_SYMBOL_GPL(udp4_lib_lookup_skb); diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index aca06094110f..2ba6a77a8815 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -315,13 +315,13 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb, __be16 sport, __be16 dport, struct udp_table *udptable) { - struct sock *sk; const struct ipv6hdr *iph = ipv6_hdr(skb); + struct sock *sk; sk = skb_steal_sock(skb); if (unlikely(sk)) return sk; - return __udp6_lib_lookup(dev_net(skb_dst(skb)->dev), &iph->saddr, sport, + return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport, &iph->daddr, dport, inet6_iif(skb), udptable, skb); } @@ -330,10 +330,8 @@ struct sock *udp6_lib_lookup_skb(struct sk_buff *skb, __be16 sport, __be16 dport) { const struct ipv6hdr *iph = ipv6_hdr(skb); - const struct net_device *dev = - skb_dst(skb) ? skb_dst(skb)->dev : skb->dev; - return __udp6_lib_lookup(dev_net(dev), &iph->saddr, sport, + return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport, &iph->daddr, dport, inet6_iif(skb), &udp_table, skb); } -- 2.20.1