net: Fix slab-out-of-bounds in inet[6]_steal_sock

Kumar reported a KASAN splat in tcp_v6_rcv:

  bash-5.2# ./test_progs -t btf_skc_cls_ingress
  ...
  [   51.810085] BUG: KASAN: slab-out-of-bounds in tcp_v6_rcv+0x2d7d/0x3440
  [   51.810458] Read of size 2 at addr ffff8881053f038c by task test_progs/226

The problem is that inet[6]_steal_sock accesses sk->sk_protocol without
accounting for request or timewait sockets. To fix this we can't just
check sock_common->skc_reuseport since that flag is present on timewait
sockets.

Instead, add a fullsock check to avoid the out of bands access of sk_protocol.

Fixes: 9c02bec95954 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign")
Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Lorenz Bauer <lmb@isovalent.com>
Link: https://lore.kernel.org/r/20230815-bpf-next-v2-1-95126eaa4c1b@isovalent.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
index 284b5ce..533a733 100644 (file)
--- a/include/net/inet6_hashtables.h
+++ b/include/net/inet6_hashtables.h
@@ -116,7 +116,7 @@ struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff,
        if (!sk)
                return NULL;
 
-       if (!prefetched)
+       if (!prefetched || !sk_fullsock(sk))
                return sk;
 
        if (sk->sk_protocol == IPPROTO_TCP) {

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 8435572..3ecfead 100644 (file)
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -462,7 +462,7 @@ struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff,
        if (!sk)
                return NULL;
 
-       if (!prefetched)
+       if (!prefetched || !sk_fullsock(sk))
                return sk;
 
        if (sk->sk_protocol == IPPROTO_TCP) {