[PATCH 3.16 064/306] netfilter: nf_tables: validate maximum value of u32 netlink attributes

Ben Hutchings
2017-02-15T23:40:37Z

From: Laura Garcia Liebana <nevola@gmail.com>

commit 36b701fae12ac763a568037e4e7c96b5727a8b3e upstream.

Fetch value and validate u32 netlink attribute. This validation is
usually required when the u32 netlink attributes are being stored in a
field whose size is smaller.

This patch revisits 4da449ae1df9 ("netfilter: nft_exthdr: Add size check
on u8 nft_exthdr attributes").

Fixes: 96518518cc41 ("netfilter: add nftables")
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Laura Garcia Liebana <nevola@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -113,6 +113,7 @@ static inline enum nft_registers nft_typ
return type == NFT_DATA_VERDICT ? NFT_REG_VERDICT : NFT_REG_1;
}

+unsigned int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest);
int nft_validate_input_register(enum nft_registers reg);
int nft_validate_output_register(enum nft_registers reg);
int nft_validate_data_load(const struct nft_ctx *ctx, enum nft_registers reg,
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3712,6 +3712,31 @@ static int nf_tables_check_loops(const s
}

/**
+ * nft_parse_u32_check - fetch u32 attribute and check for maximum value
+ *
+ * @attr: netlink attribute to fetch value from
+ * @max: maximum value to be stored in dest
+ * @dest: pointer to the variable
+ *
+ * Parse, check and store a given u32 netlink attribute into variable.
+ * This function returns -ERANGE if the value goes over maximum value.
+ * Otherwise a 0 is returned and the attribute value is stored in the
+ * destination variable.
+ */
+unsigned int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest)
+{
+ int val;
+
+ val = ntohl(nla_get_be32(attr));
+ if (val > max)
+ return -ERANGE;
+
+ *dest = val;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(nft_parse_u32_check);
+
+/**
* nft_validate_input_register - validate an expressions' input register
*
* @reg: the register number
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -54,6 +54,7 @@ static int nft_bitwise_init(const struct
{
struct nft_bitwise *priv = nft_expr_priv(expr);
struct nft_data_desc d1, d2;
+ u32 len;
int err;

if (tb[NFTA_BITWISE_SREG] == NULL ||
@@ -76,7 +77,11 @@ static int nft_bitwise_init(const struct
if (err < 0)
return err;

- priv->len = ntohl(nla_get_be32(tb[NFTA_BITWISE_LEN]));
+ err = nft_parse_u32_check(tb[NFTA_BITWISE_LEN], U8_MAX, &len);
+ if (err < 0)
+ return err;
+
+ priv->len = len;

err = nft_data_init(NULL, &priv->mask, &d1, tb[NFTA_BITWISE_MASK]);
if (err < 0)
--- a/net/netfilter/nft_byteorder.c
+++ b/net/netfilter/nft_byteorder.c
@@ -78,6 +78,7 @@ static int nft_byteorder_init(const stru
const struct nlattr * const tb[])
{
struct nft_byteorder *priv = nft_expr_priv(expr);
+ u32 size, len;
int err;

if (tb[NFTA_BYTEORDER_SREG] == NULL ||
@@ -109,11 +110,21 @@ static int nft_byteorder_init(const stru
return -EINVAL;
}

- priv->len = ntohl(nla_get_be32(tb[NFTA_BYTEORDER_LEN]));
+ err = nft_parse_u32_check(tb[NFTA_BYTEORDER_LEN], U8_MAX, &len);
+ if (err < 0)
+ return err;
+
+ priv->len = len;
+
if (priv->len == 0 || priv->len > FIELD_SIZEOF(struct nft_data, data))
return -EINVAL;

- priv->size = ntohl(nla_get_be32(tb[NFTA_BYTEORDER_SIZE]));
+ err = nft_parse_u32_check(tb[NFTA_BYTEORDER_SIZE], U8_MAX, &size);
+ if (err < 0)
+ return err;
+
+ priv->size = size;
+
switch (priv->size) {
case 2:
case 4:
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -81,6 +81,9 @@ static int nft_cmp_init(const struct nft
err = nft_data_init(NULL, &priv->data, &desc, tb[NFTA_CMP_DATA]);
BUG_ON(err < 0);

+ if (desc.len > U8_MAX)
+ return -ERANGE;
+
priv->len = desc.len;
return 0;
}
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -67,11 +67,13 @@ static int nft_exthdr_init(const struct
tb[NFTA_EXTHDR_LEN] == NULL)
return -EINVAL;

- offset = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OFFSET]));
- len = ntohl(nla_get_be32(tb[NFTA_EXTHDR_LEN]));
+ err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
+ if (err < 0)
+ return err;

- if (offset > U8_MAX || len > U8_MAX)
- return -ERANGE;
+ err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
+ if (err < 0)
+ return err;

priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
priv->offset = offset;
--- a/net/netfilter/nft_immediate.c
+++ b/net/netfilter/nft_immediate.c
@@ -57,6 +57,10 @@ static int nft_immediate_init(const stru
err = nft_data_init(ctx, &priv->data, &desc, tb[NFTA_IMMEDIATE_DATA]);
if (err < 0)
return err;
+
+ if (desc.len > U8_MAX)
+ return -ERANGE;
+
priv->dlen = desc.len;

err = nft_validate_data_load(ctx, priv->dreg, &priv->data, desc.type);