From cf6b5ffdce5a78b2fcb0e53b3a2487c490bcbf7f Mon Sep 17 00:00:00 2001 From: Phil Sutter Date: Tue, 8 Jun 2021 11:40:57 +0200 Subject: [PATCH] netfilter: nft_exthdr: Fix for unsafe packet data read While iterating through an SCTP packet's chunks, skb_header_pointer() is called for the minimum expected chunk header size. If (that part of) the skbuff is non-linear, the following memcpy() may read data past temporary buffer '_sch'. Use skb_copy_bits() instead which does the right thing in this situation. Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks") Suggested-by: Florian Westphal Signed-off-by: Phil Sutter Reviewed-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_exthdr.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c index 1b0579cb62d0..7f705b5c09de 100644 --- a/net/netfilter/nft_exthdr.c +++ b/net/netfilter/nft_exthdr.c @@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr, break; dest[priv->len / NFT_REG32_SIZE] = 0; - memcpy(dest, (char *)sch + priv->offset, priv->len); + if (skb_copy_bits(pkt->skb, offset + priv->offset, + dest, priv->len) < 0) + break; return; } offset += SCTP_PAD4(ntohs(sch->length));