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netfilter: nf_tables: fix userdata length overflow

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The NFT_USERDATA_MAXLEN is defined to 256, however we only have a u8
to store its size. Introduce a struct nft_userdata which contains a
length field and indicate its presence using a single bit in the rule.

The length field of struct nft_userdata is also a u8, however we don't
store zero sized data, so the actual length is udata->len + 1.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Patrick McHardy 2015-03-03 20:04:20 +00:00 committed by Pablo Neira Ayuso
parent 9889840f59
commit 86f1ec3231
2 changed files with 38 additions and 12 deletions
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22
include/net/netfilter/nf_tables.h
View File

@ -119,6 +119,22 @@ int nft_validate_data_load(const struct nft_ctx *ctx, enum nft_registers reg,
const struct nft_data *data,
enum nft_data_types type);
/**
* struct nft_userdata - user defined data associated with an object
*
* @len: length of the data
* @data: content
*
* The presence of user data is indicated in an object specific fashion,
* so a length of zero can't occur and the value "len" indicates data
* of length len + 1.
*/
struct nft_userdata {
u8 len;
unsigned char data[0];
};
/**
* struct nft_set_elem - generic representation of set elements
*
@ -380,7 +396,7 @@ static inline void *nft_expr_priv(const struct nft_expr *expr)
* @handle: rule handle
* @genmask: generation mask
* @dlen: length of expression data
* @ulen: length of user data (used for comments)
* @udata: user data is appended to the rule
* @data: expression data
*/
struct nft_rule {
@ -388,7 +404,7 @@ struct nft_rule {
u64 handle:42,
genmask:2,
dlen:12,
ulen:8;
udata:1;
unsigned char data[]
__attribute__((aligned(__alignof__(struct nft_expr))));
};
@ -476,7 +492,7 @@ static inline struct nft_expr *nft_expr_last(const struct nft_rule *rule)
return (struct nft_expr *)&rule->data[rule->dlen];
}
static inline void *nft_userdata(const struct nft_rule *rule)
static inline struct nft_userdata *nft_userdata(const struct nft_rule *rule)
{
return (void *)&rule->data[rule->dlen];
}

28
net/netfilter/nf_tables_api.c
View File

@ -1711,9 +1711,12 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net,
}
nla_nest_end(skb, list);
if (rule->ulen &&
nla_put(skb, NFTA_RULE_USERDATA, rule->ulen, nft_userdata(rule)))
goto nla_put_failure;
if (rule->udata) {
struct nft_userdata *udata = nft_userdata(rule);
if (nla_put(skb, NFTA_RULE_USERDATA, udata->len + 1,
udata->data) < 0)
goto nla_put_failure;
}
nlmsg_end(skb, nlh);
return 0;
@ -1896,11 +1899,12 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
struct nft_table *table;
struct nft_chain *chain;
struct nft_rule *rule, *old_rule = NULL;
struct nft_userdata *udata;
struct nft_trans *trans = NULL;
struct nft_expr *expr;
struct nft_ctx ctx;
struct nlattr *tmp;
unsigned int size, i, n, ulen = 0;
unsigned int size, i, n, ulen = 0, usize = 0;
int err, rem;
bool create;
u64 handle, pos_handle;
@ -1973,11 +1977,14 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
if (size >= 1 << 12)
goto err1;
if (nla[NFTA_RULE_USERDATA])
if (nla[NFTA_RULE_USERDATA]) {
ulen = nla_len(nla[NFTA_RULE_USERDATA]);
if (ulen > 0)
usize = sizeof(struct nft_userdata) + ulen;
}
err = -ENOMEM;
rule = kzalloc(sizeof(*rule) + size + ulen, GFP_KERNEL);
rule = kzalloc(sizeof(*rule) + size + usize, GFP_KERNEL);
if (rule == NULL)
goto err1;
@ -1985,10 +1992,13 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
rule->handle = handle;
rule->dlen = size;
rule->ulen = ulen;
rule->udata = ulen ? 1 : 0;
if (ulen)
nla_memcpy(nft_userdata(rule), nla[NFTA_RULE_USERDATA], ulen);
if (ulen) {
udata = nft_userdata(rule);
udata->len = ulen - 1;
nla_memcpy(udata->data, nla[NFTA_RULE_USERDATA], ulen);
}
expr = nft_expr_first(rule);
for (i = 0; i < n; i++) {