net: convert sock.sk_refcnt from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

This patch uses refcount_inc_not_zero() instead of
atomic_inc_not_zero_hint() due to absense of a _hint()
version of refcount API. If the hint() version must
be used, we might need to revisit API.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index bdffad8..b0bb5d0 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -1063,7 +1063,7 @@ static void raw_sock_seq_show(struct seq_file *seq, struct sock *sp, int i)
 		0, 0L, 0,
 		from_kuid_munged(seq_user_ns(seq), sock_i_uid(sp)),
 		0, sock_i_ino(sp),
-		atomic_read(&sp->sk_refcnt), sp, atomic_read(&sp->sk_drops));
+		refcount_read(&sp->sk_refcnt), sp, atomic_read(&sp->sk_drops));
 }
 
 static int raw_seq_show(struct seq_file *seq, void *v)