netfilter: nf_queue: fix possible use-after-free

Eric Dumazet says:
  The sock_hold() side seems suspect, because there is no guarantee
  that sk_refcnt is not already 0.

On failure, we cannot queue the packet and need to indicate an
error.  The packet will be dropped by the caller.

v2: split skb prefetch hunk into separate change

Fixes: 271b72c7fa82c ("udp: RCU handling for Unicast packets.")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/include/net/netfilter/nf_queue.h b/include/net/netfilter/nf_queue.h
index 9eed51e..980daa6 100644 (file)
--- a/include/net/netfilter/nf_queue.h
+++ b/include/net/netfilter/nf_queue.h
@@ -37,7 +37,7 @@ void nf_register_queue_handler(const struct nf_queue_handler *qh);
 void nf_unregister_queue_handler(void);
 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict);
 
-void nf_queue_entry_get_refs(struct nf_queue_entry *entry);
+bool nf_queue_entry_get_refs(struct nf_queue_entry *entry);
 void nf_queue_entry_free(struct nf_queue_entry *entry);
 
 static inline void init_hashrandom(u32 *jhash_initval)

diff --git a/net/netfilter/nf_queue.c b/net/netfilter/nf_queue.c
index 5ab0680..e39549c 100644 (file)
--- a/net/netfilter/nf_queue.c
+++ b/net/netfilter/nf_queue.c
@@ -96,19 +96,21 @@ static void __nf_queue_entry_init_physdevs(struct nf_queue_entry *entry)
 }
 
 /* Bump dev refs so they don't vanish while packet is out */
-void nf_queue_entry_get_refs(struct nf_queue_entry *entry)
+bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
 {
        struct nf_hook_state *state = &entry->state;
 
+       if (state->sk && !refcount_inc_not_zero(&state->sk->sk_refcnt))
+               return false;
+
        dev_hold(state->in);
        dev_hold(state->out);
-       if (state->sk)
-               sock_hold(state->sk);
 
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
        dev_hold(entry->physin);
        dev_hold(entry->physout);
 #endif
+       return true;
 }
 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
 
@@ -196,7 +198,10 @@ static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
 
        __nf_queue_entry_init_physdevs(entry);
 
-       nf_queue_entry_get_refs(entry);
+       if (!nf_queue_entry_get_refs(entry)) {
+               kfree(entry);
+               return -ENOTCONN;
+       }
 
        switch (entry->state.pf) {
        case AF_INET:

diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index ea2d9c2..64a6acb 100644 (file)
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -710,9 +710,15 @@ static struct nf_queue_entry *
 nf_queue_entry_dup(struct nf_queue_entry *e)
 {
        struct nf_queue_entry *entry = kmemdup(e, e->size, GFP_ATOMIC);
-       if (entry)
-               nf_queue_entry_get_refs(entry);
-       return entry;
+
+       if (!entry)
+               return NULL;
+
+       if (nf_queue_entry_get_refs(entry))
+               return entry;
+
+       kfree(entry);
+       return NULL;
 }
 
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)