With 16bit mask values, the first two bytes of bitwise.mask in struct nft_xt_ctx_reg are significant. Reading the first 32bit-sized field works only on Little Endian, on Big Endian the mask appears in the upper two bytes which are discarded when assigning to a 16bit variable. Fixes: ab2d5f8c7bbee ("nft-arp: add missing mask support") Signed-off-by: Phil Sutter --- Changes since v1: - Use memcpy() to avoid gcc's -Wstrict-aliasing warning --- iptables/nft-ruleparse-arp.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/iptables/nft-ruleparse-arp.c b/iptables/nft-ruleparse-arp.c index b0671cb0dfe8f..632e7ac94727c 100644 --- a/iptables/nft-ruleparse-arp.c +++ b/iptables/nft-ruleparse-arp.c @@ -90,7 +90,8 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx, if (inv) fw->arp.invflags |= IPT_INV_ARPHRD; if (reg->bitwise.set) - fw->arp.arhrd_mask = reg->bitwise.mask[0]; + memcpy(&fw->arp.arhrd_mask, reg->bitwise.mask, + sizeof(fw->arp.arhrd_mask)); break; case offsetof(struct arphdr, ar_pro): get_cmp_data(e, &ar_pro, sizeof(ar_pro), &inv); @@ -99,7 +100,8 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx, if (inv) fw->arp.invflags |= IPT_INV_PROTO; if (reg->bitwise.set) - fw->arp.arpro_mask = reg->bitwise.mask[0]; + memcpy(&fw->arp.arpro_mask, reg->bitwise.mask, + sizeof(fw->arp.arpro_mask)); break; case offsetof(struct arphdr, ar_op): get_cmp_data(e, &ar_op, sizeof(ar_op), &inv); @@ -108,7 +110,8 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx, if (inv) fw->arp.invflags |= IPT_INV_ARPOP; if (reg->bitwise.set) - fw->arp.arpop_mask = reg->bitwise.mask[0]; + memcpy(&fw->arp.arpop_mask, reg->bitwise.mask, + sizeof(fw->arp.arpop_mask)); break; case offsetof(struct arphdr, ar_hln): get_cmp_data(e, &ar_hln, sizeof(ar_hln), &inv); @@ -117,7 +120,8 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx, if (inv) fw->arp.invflags |= IPT_INV_ARPHLN; if (reg->bitwise.set) - fw->arp.arhln_mask = reg->bitwise.mask[0]; + memcpy(&fw->arp.arhln_mask, reg->bitwise.mask, + sizeof(fw->arp.arhln_mask)); break; case offsetof(struct arphdr, ar_pln): get_cmp_data(e, &ar_pln, sizeof(ar_pln), &inv); -- 2.51.0