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authorJiri Benc <jbenc@redhat.com>2019-10-09 10:31:24 +0200
committerAlexei Starovoitov <ast@kernel.org>2019-10-14 11:43:48 -0700
commit9e8acd9c44a0dd52b2922eeb82398c04e356c058 (patch)
tree5638d806575c844a9b27561ba1e93d27586602fa /net/core/lwt_bpf.c
parent33902b4a4227877896dd9368ac10f4ca0d100de5 (diff)
bpf: lwtunnel: Fix reroute supplying invalid dst
The dst in bpf_input() has lwtstate field set. As it is of the LWTUNNEL_ENCAP_BPF type, lwtstate->data is struct bpf_lwt. When the bpf program returns BPF_LWT_REROUTE, ip_route_input_noref is directly called on this skb. This causes invalid memory access, as ip_route_input_slow calls skb_tunnel_info(skb) that expects the dst->lwstate->data to be struct ip_tunnel_info. This results to struct bpf_lwt being accessed as struct ip_tunnel_info. Drop the dst before calling the IP route input functions (both for IPv4 and IPv6). Reported by KASAN. Fixes: 3bd0b15281af ("bpf: add handling of BPF_LWT_REROUTE to lwt_bpf.c") Signed-off-by: Jiri Benc <jbenc@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Peter Oskolkov <posk@google.com> Link: https://lore.kernel.org/bpf/111664d58fe4e9dd9c8014bb3d0b2dab93086a9e.1570609794.git.jbenc@redhat.com
Diffstat (limited to 'net/core/lwt_bpf.c')
-rw-r--r--net/core/lwt_bpf.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c
index f93785e5833c..74cfb8b5ab33 100644
--- a/net/core/lwt_bpf.c
+++ b/net/core/lwt_bpf.c
@@ -88,11 +88,16 @@ static int bpf_lwt_input_reroute(struct sk_buff *skb)
int err = -EINVAL;
if (skb->protocol == htons(ETH_P_IP)) {
+ struct net_device *dev = skb_dst(skb)->dev;
struct iphdr *iph = ip_hdr(skb);
+ dev_hold(dev);
+ skb_dst_drop(skb);
err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
- iph->tos, skb_dst(skb)->dev);
+ iph->tos, dev);
+ dev_put(dev);
} else if (skb->protocol == htons(ETH_P_IPV6)) {
+ skb_dst_drop(skb);
err = ipv6_stub->ipv6_route_input(skb);
} else {
err = -EAFNOSUPPORT;