CVE-2021-47397

In the Linux kernel, the following vulnerability has been resolved: sctp:
break out if skb_header_pointer returns NULL in sctp_rcv_ootb We should
always check if skb_header_pointer’s return is NULL before using it,
otherwise it may cause null-ptr-deref, as syzbot reported: KASAN:
null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP:
0010:sctp_rcv_ootb net/sctp/input.c:705 [inline] RIP:
0010:sctp_rcv+0x1d84/0x3220 net/sctp/input.c:196 Call Trace: <IRQ>
sctp6_rcv+0x38/0x60 net/sctp/ipv6.c:1109
ip6_protocol_deliver_rcu+0x2e9/0x1ca0 net/ipv6/ip6_input.c:422
ip6_input_finish+0x62/0x170 net/ipv6/ip6_input.c:463 NF_HOOK
include/linux/netfilter.h:307 [inline] NF_HOOK
include/linux/netfilter.h:301 [inline] ip6_input+0x9c/0xd0
net/ipv6/ip6_input.c:472 dst_input include/net/dst.h:460 [inline]
ip6_rcv_finish net/ipv6/ip6_input.c:76 [inline] NF_HOOK
include/linux/netfilter.h:307 [inline] NF_HOOK
include/linux/netfilter.h:301 [inline] ipv6_rcv+0x28c/0x3c0
net/ipv6/ip6_input.c:297