socket, bpf: fix possible use after free
Starting from linux-4.4, 3WHS no longer takes the listener lock.
Since this time, we might hit a use-after-free in sk_filter_charge(),
if the filter we got in the memcpy() of the listener content
just happened to be replaced by a thread changing listener BPF filter.
To fix this, we need to make sure the filter refcount is not already
zero before incrementing it again.
Fixes: e994b2f0fb
("tcp: do not lock listener to process SYN packets")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
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@ -989,10 +989,14 @@ static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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{
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{
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bool ret = __sk_filter_charge(sk, fp);
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if (!refcount_inc_not_zero(&fp->refcnt))
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if (ret)
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return false;
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refcount_inc(&fp->refcnt);
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return ret;
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if (!__sk_filter_charge(sk, fp)) {
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sk_filter_release(fp);
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return false;
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}
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return true;
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}
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}
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static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
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static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
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@ -1684,13 +1684,16 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
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sock_reset_flag(newsk, SOCK_DONE);
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sock_reset_flag(newsk, SOCK_DONE);
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filter = rcu_dereference_protected(newsk->sk_filter, 1);
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rcu_read_lock();
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filter = rcu_dereference(sk->sk_filter);
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if (filter != NULL)
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if (filter != NULL)
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/* though it's an empty new sock, the charging may fail
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/* though it's an empty new sock, the charging may fail
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* if sysctl_optmem_max was changed between creation of
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* if sysctl_optmem_max was changed between creation of
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* original socket and cloning
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* original socket and cloning
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*/
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*/
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is_charged = sk_filter_charge(newsk, filter);
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is_charged = sk_filter_charge(newsk, filter);
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RCU_INIT_POINTER(newsk->sk_filter, filter);
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rcu_read_unlock();
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if (unlikely(!is_charged || xfrm_sk_clone_policy(newsk, sk))) {
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if (unlikely(!is_charged || xfrm_sk_clone_policy(newsk, sk))) {
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/* We need to make sure that we don't uncharge the new
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/* We need to make sure that we don't uncharge the new
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