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: dbb5281a1f84 ("netfilter: nf_tables: add support for matching IPv4 options")
Fixes: c078ca3b0c5b ("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>

diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 07782836fad6ead16711db91117d837abbf66765..3c48cdc8935df7030e983581c56bd0957d71175f 100644 (file)
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -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;