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netfilter: nfnetlink: Remove VLA usage 

In the quest to remove all stack VLA usage from the kernel[1], this
allocates the maximum size expected for all possible attrs and adds
sanity-checks at both registration and usage to make sure nothing
gets out of sync.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Kees Cook 2018-05-30 12:17:56 -07:00 committed by Pablo Neira Ayuso
parent 2a79fd3908
commit 7b7744e2aa
1 changed files with 23 additions and 2 deletions
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25
net/netfilter/nfnetlink.c
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@ -38,6 +38,8 @@ MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
rcu_dereference_protected(table[(id)].subsys, \
lockdep_nfnl_is_held((id)))
#define NFNL_MAX_ATTR_COUNT 32
static struct {
struct mutex mutex;
const struct nfnetlink_subsystem __rcu *subsys;
@ -77,6 +79,13 @@ EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
{
u8 cb_id;
/* Sanity-check attr_count size to avoid stack buffer overflow. */
for (cb_id = 0; cb_id < n->cb_count; cb_id++)
if (WARN_ON(n->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT))
return -EINVAL;
nfnl_lock(n->subsys_id);
if (table[n->subsys_id].subsys) {
nfnl_unlock(n->subsys_id);
@ -186,11 +195,17 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
{
int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
struct nlattr *attr = (void *)nlh + min_len;
int attrlen = nlh->nlmsg_len - min_len;
__u8 subsys_id = NFNL_SUBSYS_ID(type);
/* Sanity-check NFNL_MAX_ATTR_COUNT */
if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
rcu_read_unlock();
return -ENOMEM;
}
err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen,
ss->cb[cb_id].policy, extack);
if (err < 0) {
@ -387,10 +402,16 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
{
int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
struct nlattr *attr = (void *)nlh + min_len;
int attrlen = nlh->nlmsg_len - min_len;
/* Sanity-check NFTA_MAX_ATTR */
if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
err = -ENOMEM;
goto ack;
}
err = nla_parse(cda, ss->cb[cb_id].attr_count, attr,
attrlen, ss->cb[cb_id].policy, NULL);
if (err < 0)