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netfilter: nf_tables: add __nft_chain_type_get()

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This new helper function validates that unknown family and chain type
coming from userspace do not trigger an out-of-bound array access. Bail
out in case __nft_chain_type_get() returns NULL from
nft_chain_parse_hook().

Fixes: 9370761c56 ("netfilter: nf_tables: convert built-in tables/chains to chain types")
Reported-by: syzbot+156a04714799b1d480bc@syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2020-01-21 16:07:00 +01:00
parent c83de17dd6
commit 826035498e
1 changed files with 21 additions and 8 deletions
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29
net/netfilter/nf_tables_api.c
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@ -552,15 +552,28 @@ static inline u64 nf_tables_alloc_handle(struct nft_table *table)
static const struct nft_chain_type *chain_type[NFPROTO_NUMPROTO][NFT_CHAIN_T_MAX];
static const struct nft_chain_type *
__nft_chain_type_get(u8 family, enum nft_chain_types type)
{
if (family >= NFPROTO_NUMPROTO ||
type >= NFT_CHAIN_T_MAX)
return NULL;
return chain_type[family][type];
}
static const struct nft_chain_type *
__nf_tables_chain_type_lookup(const struct nlattr *nla, u8 family)
{
const struct nft_chain_type *type;
int i;
for (i = 0; i < NFT_CHAIN_T_MAX; i++) {
if (chain_type[family][i] != NULL &&
!nla_strcmp(nla, chain_type[family][i]->name))
return chain_type[family][i];
type = __nft_chain_type_get(family, i);
if (!type)
continue;
if (!nla_strcmp(nla, type->name))
return type;
}
return NULL;
}
@ -1162,11 +1175,8 @@ static void nf_tables_table_destroy(struct nft_ctx *ctx)
void nft_register_chain_type(const struct nft_chain_type *ctype)
{
if (WARN_ON(ctype->family >= NFPROTO_NUMPROTO))
return;
nfnl_lock(NFNL_SUBSYS_NFTABLES);
if (WARN_ON(chain_type[ctype->family][ctype->type] != NULL)) {
if (WARN_ON(__nft_chain_type_get(ctype->family, ctype->type))) {
nfnl_unlock(NFNL_SUBSYS_NFTABLES);
return;
}
@ -1768,7 +1778,10 @@ static int nft_chain_parse_hook(struct net *net,
hook->num = ntohl(nla_get_be32(ha[NFTA_HOOK_HOOKNUM]));
hook->priority = ntohl(nla_get_be32(ha[NFTA_HOOK_PRIORITY]));
type = chain_type[family][NFT_CHAIN_T_DEFAULT];
type = __nft_chain_type_get(family, NFT_CHAIN_T_DEFAULT);
if (!type)
return -EOPNOTSUPP;
if (nla[NFTA_CHAIN_TYPE]) {
type = nf_tables_chain_type_lookup(net, nla[NFTA_CHAIN_TYPE],
family, autoload);