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authorEric Dumazet <edumazet@google.com>2017-10-02 12:20:51 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-12 11:51:23 +0200
commit02f7e4101092b88e57c73171174976c8a72a3eba (patch)
parent95206ea376b9ed43ff7cac7f944f654b4314f754 (diff)
socket, bpf: fix possible use after free
[ Upstream commit eefca20eb20c66b06cf5ed09b49b1a7caaa27b7b ] 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: e994b2f0fb92 ("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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2 files changed, 17 insertions, 3 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index 4eb4ce0aeef4..bfeedbbde214 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -937,20 +937,31 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
/* try to charge the socket memory if there is space available
* return true on success
-bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
+static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
u32 filter_size = bpf_prog_size(fp->prog->len);
/* same check as in sock_kmalloc() */
if (filter_size <= sysctl_optmem_max &&
atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
- atomic_inc(&fp->refcnt);
atomic_add(filter_size, &sk->sk_omem_alloc);
return true;
return false;
+bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
+ if (!atomic_inc_not_zero(&fp->refcnt))
+ return false;
+ if (!__sk_filter_charge(sk, fp)) {
+ sk_filter_release(fp);
+ return false;
+ }
+ return true;
static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
struct sock_filter *old_prog;
diff --git a/net/core/sock.c b/net/core/sock.c
index 231c38d91855..2a77cc50f021 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1528,13 +1528,16 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
sock_reset_flag(newsk, SOCK_DONE);
- filter = rcu_dereference_protected(newsk->sk_filter, 1);
+ rcu_read_lock();
+ filter = rcu_dereference(sk->sk_filter);
if (filter != NULL)
/* though it's an empty new sock, the charging may fail
* if sysctl_optmem_max was changed between creation of
* original socket and cloning
is_charged = sk_filter_charge(newsk, filter);
+ RCU_INIT_POINTER(newsk->sk_filter, filter);
+ rcu_read_unlock();
if (unlikely(!is_charged || xfrm_sk_clone_policy(newsk, sk))) {
/* We need to make sure that we don't uncharge the new