[PATCH 4.9 15/32] netfilter: nf_queue: fix possible use-after-free

Greg Kroah-Hartman
2022-03-07T09:19:42Z

From: Florian Westphal <fw@strlen.de>

commit c3873070247d9e3c7a6b0cf9bf9b45e8018427b1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/netfilter/nf_queue.h | 2 +-
net/netfilter/nf_queue.c | 12 ++++++++++--
net/netfilter/nfnetlink_queue.c | 12 +++++++++---
3 files changed, 20 insertions(+), 6 deletions(-)

--- a/include/net/netfilter/nf_queue.h
+++ b/include/net/netfilter/nf_queue.h
@@ -31,7 +31,7 @@ void nf_register_queue_handler(struct ne
void nf_unregister_queue_handler(struct net *net);
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_release_refs(struct nf_queue_entry *entry);

static inline void init_hashrandom(u32 *jhash_initval)
--- a/net/netfilter/nf_queue.c
+++ b/net/netfilter/nf_queue.c
@@ -80,10 +80,13 @@ void nf_queue_entry_release_refs(struct
EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);

/* 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 && !atomic_inc_not_zero(&state->sk->sk_refcnt))
+ return false;
+
if (state->in)
dev_hold(state->in);
if (state->out)
@@ -102,6 +105,7 @@ void nf_queue_entry_get_refs(struct nf_q
dev_hold(physdev);
}
#endif
+ return true;
}
EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);

@@ -148,7 +152,11 @@ static int __nf_queue(struct sk_buff *sk
.size = sizeof(*entry) + afinfo->route_key_size,
};

- nf_queue_entry_get_refs(entry);
+ if (!nf_queue_entry_get_refs(entry)) {
+ kfree(entry);
+ return -ENOTCONN;
+ }
+
skb_dst_force(skb);
afinfo->saveroute(skb, entry);
status = qh->outfn(entry, queuenum);
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -673,9 +673,15 @@ 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)