[PATCH 5.10 39/86] netfilter: nft_cmp: optimize comparison for 16-bytes

Greg Kroah-Hartman
2022-08-29T11:38:30Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 23f68d462984bfda47c7bf663dca347e8e3df549 ]

Allow up to 16-byte comparisons with a new cmp fast version. Use two
64-bit words and calculate the mask representing the bits to be
compared. Make sure the comparison is 64-bit aligned and avoid
out-of-bound memory access on registers.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/netfilter/nf_tables_core.h | 9 +++
net/netfilter/nf_tables_core.c | 16 ++++
net/netfilter/nft_cmp.c | 102 ++++++++++++++++++++++++-
3 files changed, 125 insertions(+), 2 deletions(-)

diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
index fd10a7862fdc6..ce75121782bf7 100644
--- a/include/net/netfilter/nf_tables_core.h
+++ b/include/net/netfilter/nf_tables_core.h
@@ -38,6 +38,14 @@ struct nft_cmp_fast_expr {
bool inv;
};

+struct nft_cmp16_fast_expr {
+ struct nft_data data;
+ struct nft_data mask;
+ u8 sreg;
+ u8 len;
+ bool inv;
+};
+
struct nft_immediate_expr {
struct nft_data data;
u8 dreg;
@@ -55,6 +63,7 @@ static inline u32 nft_cmp_fast_mask(unsigned int len)
}

extern const struct nft_expr_ops nft_cmp_fast_ops;
+extern const struct nft_expr_ops nft_cmp16_fast_ops;

struct nft_payload {
enum nft_payload_bases base:8;
diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 6dd27c8cd4253..9dc18429ed875 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -67,6 +67,20 @@ static void nft_cmp_fast_eval(const struct nft_expr *expr,
regs->verdict.code = NFT_BREAK;
}

+static void nft_cmp16_fast_eval(const struct nft_expr *expr,
+ struct nft_regs *regs)
+{
+ const struct nft_cmp16_fast_expr *priv = nft_expr_priv(expr);
+ const u64 *reg_data = (const u64 *)&regs->data[priv->sreg];
+ const u64 *mask = (const u64 *)&priv->mask;
+ const u64 *data = (const u64 *)&priv->data;
+
+ if (((reg_data[0] & mask[0]) == data[0] &&
+ ((reg_data[1] & mask[1]) == data[1])) ^ priv->inv)
+ return;
+ regs->verdict.code = NFT_BREAK;
+}
+
static noinline void __nft_trace_verdict(struct nft_traceinfo *info,
const struct nft_chain *chain,
const struct nft_regs *regs)
@@ -215,6 +229,8 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
nft_rule_for_each_expr(expr, last, rule) {
if (expr->ops == &nft_cmp_fast_ops)
nft_cmp_fast_eval(expr, &regs);
+ else if (expr->ops == &nft_cmp16_fast_ops)
+ nft_cmp16_fast_eval(expr, &regs);
else if (expr->ops == &nft_bitwise_fast_ops)
nft_bitwise_fast_eval(expr, &regs);
else if (expr->ops != &nft_payload_fast_ops ||
diff --git a/net/netfilter/nft_cmp.c b/net/netfilter/nft_cmp.c
index 47b6d05f1ae69..917072af09df9 100644
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -272,12 +272,103 @@ const struct nft_expr_ops nft_cmp_fast_ops = {
.offload = nft_cmp_fast_offload,
};

+static u32 nft_cmp_mask(u32 bitlen)
+{
+ return (__force u32)cpu_to_le32(~0U >> (sizeof(u32) * BITS_PER_BYTE - bitlen));
+}
+
+static void nft_cmp16_fast_mask(struct nft_data *data, unsigned int bitlen)
+{
+ int len = bitlen / BITS_PER_BYTE;
+ int i, words = len / sizeof(u32);
+
+ for (i = 0; i < words; i++) {
+ data->data[i] = 0xffffffff;
+ bitlen -= sizeof(u32) * BITS_PER_BYTE;
+ }
+
+ if (len % sizeof(u32))
+ data->data[i++] = nft_cmp_mask(bitlen);
+
+ for (; i < 4; i++)
+ data->data[i] = 0;
+}
+
+static int nft_cmp16_fast_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_cmp16_fast_expr *priv = nft_expr_priv(expr);
+ struct nft_data_desc desc;
+ int err;
+
+ err = nft_data_init(NULL, &priv->data, sizeof(priv->data), &desc,
+ tb[NFTA_CMP_DATA]);
+ if (err < 0)
+ return err;
+
+ err = nft_parse_register_load(tb[NFTA_CMP_SREG], &priv->sreg, desc.len);
+ if (err < 0)
+ return err;
+
+ nft_cmp16_fast_mask(&priv->mask, desc.len * BITS_PER_BYTE);
+ priv->inv = ntohl(nla_get_be32(tb[NFTA_CMP_OP])) != NFT_CMP_EQ;
+ priv->len = desc.len;
+
+ return 0;
+}
+
+static int nft_cmp16_fast_offload(struct nft_offload_ctx *ctx,
+ struct nft_flow_rule *flow,
+ const struct nft_expr *expr)
+{
+ const struct nft_cmp16_fast_expr *priv = nft_expr_priv(expr);
+ struct nft_cmp_expr cmp = {
+ .data = priv->data,
+ .sreg = priv->sreg,
+ .len = priv->len,
+ .op = priv->inv ? NFT_CMP_NEQ : NFT_CMP_EQ,
+ };
+
+ return __nft_cmp_offload(ctx, flow, &cmp);
+}
+
+static int nft_cmp16_fast_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+ const struct nft_cmp16_fast_expr *priv = nft_expr_priv(expr);
+ enum nft_cmp_ops op = priv->inv ? NFT_CMP_NEQ : NFT_CMP_EQ;
+
+ if (nft_dump_register(skb, NFTA_CMP_SREG, priv->sreg))
+ goto nla_put_failure;
+ if (nla_put_be32(skb, NFTA_CMP_OP, htonl(op)))
+ goto nla_put_failure;
+
+ if (nft_data_dump(skb, NFTA_CMP_DATA, &priv->data,
+ NFT_DATA_VALUE, priv->len) < 0)
+ goto nla_put_failure;
+ return 0;
+
+nla_put_failure:
+ return -1;
+}
+
+
+const struct nft_expr_ops nft_cmp16_fast_ops = {
+ .type = &nft_cmp_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_cmp16_fast_expr)),
+ .eval = NULL, /* inlined */
+ .init = nft_cmp16_fast_init,
+ .dump = nft_cmp16_fast_dump,
+ .offload = nft_cmp16_fast_offload,
+};
+
static const struct nft_expr_ops *
nft_cmp_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
{
struct nft_data_desc desc;
struct nft_data data;
enum nft_cmp_ops op;
+ u8 sreg;
int err;

if (tb[NFTA_CMP_SREG] == NULL ||
@@ -306,9 +397,16 @@ nft_cmp_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
if (desc.type != NFT_DATA_VALUE)
goto err1;

- if (desc.len <= sizeof(u32) && (op == NFT_CMP_EQ || op == NFT_CMP_NEQ))
- return &nft_cmp_fast_ops;
+ sreg = ntohl(nla_get_be32(tb[NFTA_CMP_SREG]));

+ if (op == NFT_CMP_EQ || op == NFT_CMP_NEQ) {
+ if (desc.len <= sizeof(u32))
+ return &nft_cmp_fast_ops;
+ else if (desc.len <= sizeof(data) &&
+ ((sreg >= NFT_REG_1 && sreg <= NFT_REG_4) ||
+ (sreg >= NFT_REG32_00 && sreg <= NFT_REG32_12 && sreg % 2 == 0)))
+ return &nft_cmp16_fast_ops;
+ }
return &nft_cmp_ops;
err1:
nft_data_release(&data, desc.type);
--
2.35.1