Commit b4283366 authored Aug 04, 2020 by Stephen Suryaputra Committed by Pablo Neira Ayuso Aug 10, 2020

netfilter: nf_tables: nft_exthdr: the presence return value should be little-endian



On big-endian machine, the returned register data when the exthdr is
present is not being compared correctly because little-endian is
assumed. The function nft_cmp_fast_mask(), called by nft_cmp_fast_eval()
and nft_cmp_fast_init(), calls cpu_to_le32().

The following dump also shows that little endian is assumed:

$ nft --debug=netlink add rule ip recordroute forward ip option rr exists counter
ip
  [ exthdr load ipv4 1b @ 7 + 0 present => reg 1 ]
  [ cmp eq reg 1 0x01000000 ]
  [ counter pkts 0 bytes 0 ]

Lastly, debug print in nft_cmp_fast_init() and nft_cmp_fast_eval() when
RR option exists in the packet shows that the comparison fails because
the assumption:

nft_cmp_fast_init:189 priv->sreg=4 desc.len=8 mask=0xff000000 data.data[0]=0x10003e0
nft_cmp_fast_eval:57 regs->data[priv->sreg=4]=0x1 mask=0xff000000 priv->data=0x1000000

v2: use nft_reg_store8() instead (Florian Westphal). Also to avoid the
    warnings reported by kernel test robot.

Fixes: dbb5281a ("netfilter: nf_tables: add support for matching IPv4 options")
Fixes: c078ca3b ("netfilter: nft_exthdr: Add support for existence check")
Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 7c7ab580

net/netfilter/nft_exthdr.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -44,7 +44,7 @@ static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,

		err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
		if (priv->flags & NFT_EXTHDR_F_PRESENT) {
		*dest = (err >= 0);
		nft_reg_store8(dest, err >= 0);
		return;
		} else if (err < 0) {
		goto err;
		@@ -141,7 +141,7 @@ static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,

		err = ipv4_find_option(nft_net(pkt), skb, &offset, priv->type);
		if (priv->flags & NFT_EXTHDR_F_PRESENT) {
		*dest = (err >= 0);
		nft_reg_store8(dest, err >= 0);
		return;
		} else if (err < 0) {
		goto err;