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| author | Eric Dumazet <edumazet@google.com> | 2017-10-02 19:20:51 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-12 09:51:23 (GMT) |
| commit | 02f7e4101092b88e57c73171174976c8a72a3eba (patch) | |
| tree | 4271b5c0a7e8f6b27477451a08cd2e76ab474b33 /net | |
| parent | 95206ea376b9ed43ff7cac7f944f654b4314f754 (diff) | |
| download | linux-02f7e4101092b88e57c73171174976c8a72a3eba.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 | 15 | ||||
| -rw-r--r-- | net/core/sock.c | 5 |
2 files changed, 17 insertions, 3 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 4eb4ce0..bfeedbb 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 231c38d..2a77cc5 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); skb_queue_head_init(&newsk->sk_error_queue); - 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 |