diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-10-02 22:20:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-12 12:56:07 +0300 |
| commit | 83c46af1d5e92d188649891f86d6c12219f45f91 (patch) | |
| tree | 600a4aa46ddbbba103b82042ffb8b5bc8ede2da5 /net | |
| parent | d7a268ea8624115cd4b1ddd29fc410965e4b0950 (diff) | |
| download | linux-83c46af1d5e92d188649891f86d6c12219f45f91.tar.xz | |
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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/filter.c | 12 | ||||
| -rw-r--r-- | net/core/sock.c | 5 |
2 files changed, 12 insertions, 5 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 169974998c76..18d591f1ae5a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -975,10 +975,14 @@ static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp) bool sk_filter_charge(struct sock *sk, struct sk_filter *fp) { - bool ret = __sk_filter_charge(sk, fp); - if (ret) - refcount_inc(&fp->refcnt); - return ret; + if (!refcount_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) diff --git a/net/core/sock.c b/net/core/sock.c index b22228901a11..0967da925022 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1675,13 +1675,16 @@ 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 |