Revert "socket, bpf: fix possible use after free"

This reverts commit 02f7e4101092b88e57c73171174976c8a72a3eba, which was
commit 02f7e4101092b88e57c73171174976c8a72a3eba upstream

Turns out the backport to 4.9 was broken.

Reported-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/core/filter.c b/net/core/filter.c
index bfeedbb..4eb4ce0 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -937,31 +937,20 @@ 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
  */
-static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
+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 2a77cc5..231c38d 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1528,16 +1528,13 @@ 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);
 
-               rcu_read_lock();
-               filter = rcu_dereference(sk->sk_filter);
+               filter = rcu_dereference_protected(newsk->sk_filter, 1);
                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