From: Martin KaFai Lau <kafai@fb.com>
Date: Tue, 15 Sep 2020 11:29:59 -0700
Subject: bpf: Bpf_skc_to_* casting helpers require a NULL check on sk
Patch-mainline: v5.9-rc7
Git-commit: 8c33dadc3e0eef1599811a55d748a0b95da0317d
References: bsc#1177028

The bpf_skc_to_* type casting helpers are available to
BPF_PROG_TYPE_TRACING.  The traced PTR_TO_BTF_ID may be NULL.
For example, the skb->sk may be NULL.  Thus, these casting helpers
need to check "!sk" also and this patch fixes them.

Fixes: 0d4fad3e57df ("bpf: Add bpf_skc_to_udp6_sock() helper")
Fixes: 478cfbdf5f13 ("bpf: Add bpf_skc_to_{tcp, tcp_timewait, tcp_request}_sock() helpers")
Fixes: af7ec1383361 ("bpf: Add bpf_skc_to_tcp6_sock() helper")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200915182959.241101-1-kafai@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
 net/core/filter.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -9537,7 +9537,7 @@ BPF_CALL_1(bpf_skc_to_tcp6_sock, struct
 	 * trigger an explicit type generation here.
 	 */
 	BTF_TYPE_EMIT(struct tcp6_sock);
-	if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP &&
+	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP &&
 	    sk->sk_family == AF_INET6)
 		return (unsigned long)sk;
 
@@ -9555,7 +9555,7 @@ const struct bpf_func_proto bpf_skc_to_t
 
 BPF_CALL_1(bpf_skc_to_tcp_sock, struct sock *, sk)
 {
-	if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
+	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
 		return (unsigned long)sk;
 
 	return (unsigned long)NULL;
@@ -9573,12 +9573,12 @@ const struct bpf_func_proto bpf_skc_to_t
 BPF_CALL_1(bpf_skc_to_tcp_timewait_sock, struct sock *, sk)
 {
 #ifdef CONFIG_INET
-	if (sk->sk_prot == &tcp_prot && sk->sk_state == TCP_TIME_WAIT)
+	if (sk && sk->sk_prot == &tcp_prot && sk->sk_state == TCP_TIME_WAIT)
 		return (unsigned long)sk;
 #endif
 
 #if IS_BUILTIN(CONFIG_IPV6)
-	if (sk->sk_prot == &tcpv6_prot && sk->sk_state == TCP_TIME_WAIT)
+	if (sk && sk->sk_prot == &tcpv6_prot && sk->sk_state == TCP_TIME_WAIT)
 		return (unsigned long)sk;
 #endif
 
@@ -9597,12 +9597,12 @@ const struct bpf_func_proto bpf_skc_to_t
 BPF_CALL_1(bpf_skc_to_tcp_request_sock, struct sock *, sk)
 {
 #ifdef CONFIG_INET
-	if (sk->sk_prot == &tcp_prot  && sk->sk_state == TCP_NEW_SYN_RECV)
+	if (sk && sk->sk_prot == &tcp_prot && sk->sk_state == TCP_NEW_SYN_RECV)
 		return (unsigned long)sk;
 #endif
 
 #if IS_BUILTIN(CONFIG_IPV6)
-	if (sk->sk_prot == &tcpv6_prot && sk->sk_state == TCP_NEW_SYN_RECV)
+	if (sk && sk->sk_prot == &tcpv6_prot && sk->sk_state == TCP_NEW_SYN_RECV)
 		return (unsigned long)sk;
 #endif
 
@@ -9624,7 +9624,7 @@ BPF_CALL_1(bpf_skc_to_udp6_sock, struct
 	 * trigger an explicit type generation here.
 	 */
 	BTF_TYPE_EMIT(struct udp6_sock);
-	if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_UDP &&
+	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_UDP &&
 	    sk->sk_type == SOCK_DGRAM && sk->sk_family == AF_INET6)
 		return (unsigned long)sk;