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