[PATCH v30 18/28] LSM: security_secid_to_secctx in netlink netfilter

Casey Schaufler
2021-11-24T02:05:45Z

Change netlink netfilter interfaces to use lsmcontext
pointers, and remove scaffolding.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: netdev@vger.kernel.org
Cc: netfilter-devel@vger.kernel.org
---
net/netfilter/nfnetlink_queue.c | 37 +++++++++++++--------------------
1 file changed, 14 insertions(+), 23 deletions(-)

diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index f19897b3cf39..69343275c54b 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -301,15 +301,13 @@ static int nfqnl_put_sk_uidgid(struct sk_buff *skb, struct sock *sk)
return -1;
}

-static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, char **secdata)
+static void nfqnl_get_sk_secctx(struct sk_buff *skb, struct lsmcontext *context)
{
- u32 seclen = 0;
#if IS_ENABLED(CONFIG_NETWORK_SECMARK)
struct lsmblob blob;
- struct lsmcontext context = { };

if (!skb || !sk_fullsock(skb->sk))
- return 0;
+ return;

read_lock_bh(&skb->sk->sk_callback_lock);

@@ -318,14 +316,12 @@ static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, char **secdata)
* blob. security_secid_to_secctx() will know which security
* module to use to create the secctx. */
lsmblob_init(&blob, skb->secmark);
- security_secid_to_secctx(&blob, &context);
- *secdata = context.context;
+ security_secid_to_secctx(&blob, context);
}

read_unlock_bh(&skb->sk->sk_callback_lock);
- seclen = context.len;
#endif
- return seclen;
+ return;
}

static u32 nfqnl_get_bridge_size(struct nf_queue_entry *entry)
@@ -397,12 +393,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
struct net_device *indev;
struct net_device *outdev;
struct nf_conn *ct = NULL;
+ struct lsmcontext context = { };
enum ip_conntrack_info ctinfo;
struct nfnl_ct_hook *nfnl_ct;
bool csum_verify;
- struct lsmcontext scaff; /* scaffolding */
- char *secdata = NULL;
- u32 seclen = 0;

size = nlmsg_total_size(sizeof(struct nfgenmsg))
+ nla_total_size(sizeof(struct nfqnl_msg_packet_hdr))
@@ -470,9 +464,9 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
}

if ((queue->flags & NFQA_CFG_F_SECCTX) && entskb->sk) {
- seclen = nfqnl_get_sk_secctx(entskb, &secdata);
- if (seclen)
- size += nla_total_size(seclen);
+ nfqnl_get_sk_secctx(entskb, &context);
+ if (context.len)
+ size += nla_total_size(context.len);
}

skb = alloc_skb(size, GFP_ATOMIC);
@@ -602,7 +596,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
nfqnl_put_sk_uidgid(skb, entskb->sk) < 0)
goto nla_put_failure;

- if (seclen && nla_put(skb, NFQA_SECCTX, seclen, secdata))
+ if (context.len &&
+ nla_put(skb, NFQA_SECCTX, context.len, context.context))
goto nla_put_failure;

if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0)
@@ -630,10 +625,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
}

nlh->nlmsg_len = skb->len;
- if (seclen) {
- lsmcontext_init(&scaff, secdata, seclen, 0);
- security_release_secctx(&scaff);
- }
+ if (context.len)
+ security_release_secctx(&context);
return skb;

nla_put_failure:
@@ -641,10 +634,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
kfree_skb(skb);
net_err_ratelimited("nf_queue: error creating packet message\n");
nlmsg_failure:
- if (seclen) {
- lsmcontext_init(&scaff, secdata, seclen, 0);
- security_release_secctx(&scaff);
- }
+ if (context.len)
+ security_release_secctx(&context);
return NULL;