From: Xin Long lucien.xin@gmail.com

mainline inclusion from mainline-v5.15-rc4 commit f7e745f8e94492a8ac0b0a26e25f2b19d342918f category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4O3 CVE: CVE-2021-47397

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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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

Fixes: 3acb50c18d8d ("sctp: delay as much as possible skb_linearize") Reported-by: syzbot+581aff2ae6b860625116@syzkaller.appspotmail.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Cheng Yu serein.chengyu@huawei.com --- net/sctp/input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/input.c b/net/sctp/input.c index e6cc81a12f36..354a2eb84e14 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -687,7 +687,7 @@ static int sctp_rcv_ootb(struct sk_buff *skb) ch = skb_header_pointer(skb, offset, sizeof(*ch), &_ch);

/* Break out if chunk length is less then minimal. */ - if (ntohs(ch->length) < sizeof(_ch)) + if (!ch || ntohs(ch->length) < sizeof(_ch)) break;

ch_end = offset + SCTP_PAD4(ntohs(ch->length));