[PATCH net] net/packet: move reference count in packet_sock to 64 bits

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

In some potential instances the reference count on struct packet_sock
could be saturated and cause overflows which gets the kernel a bit
confused.  To prevent this, move to a 64bit atomic reference count to
prevent the possibility of this type of overflow.

Because we can not handle saturation, using refcount_t is not possible
in this place.  Maybe someday in the future if it changes could it be
used.

Original version from Daniel after I did it wrong, I've provided a
changelog.

Reported-by: "The UK's National Cyber Security Centre (NCSC)" <security@ncsc.gov.uk>
Cc: stable <stable@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/packet/af_packet.c | 16 ++++++++--------
 net/packet/internal.h  |  2 +-
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a84e00b5904b..9356b661c3d9 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4300,7 +4300,7 @@ static void packet_mm_open(struct vm_area_struct *vma)
 	struct sock *sk = sock->sk;
 
 	if (sk)
-		atomic_inc(&pkt_sk(sk)->mapped);
+		atomic64_inc(&pkt_sk(sk)->mapped);
 }
 
 static void packet_mm_close(struct vm_area_struct *vma)
@@ -4310,7 +4310,7 @@ static void packet_mm_close(struct vm_area_struct *vma)
 	struct sock *sk = sock->sk;
 
 	if (sk)
-		atomic_dec(&pkt_sk(sk)->mapped);
+		atomic64_dec(&pkt_sk(sk)->mapped);
 }
 
 static const struct vm_operations_struct packet_mmap_ops = {
@@ -4405,7 +4405,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 
 	err = -EBUSY;
 	if (!closing) {
-		if (atomic_read(&po->mapped))
+		if (atomic64_read(&po->mapped))
 			goto out;
 		if (packet_read_pending(rb))
 			goto out;
@@ -4508,7 +4508,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 
 	err = -EBUSY;
 	mutex_lock(&po->pg_vec_lock);
-	if (closing || atomic_read(&po->mapped) == 0) {
+	if (closing || atomic64_read(&po->mapped) == 0) {
 		err = 0;
 		spin_lock_bh(&rb_queue->lock);
 		swap(rb->pg_vec, pg_vec);
@@ -4526,9 +4526,9 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 		po->prot_hook.func = (po->rx_ring.pg_vec) ?
 						tpacket_rcv : packet_rcv;
 		skb_queue_purge(rb_queue);
-		if (atomic_read(&po->mapped))
-			pr_err("packet_mmap: vma is busy: %d\n",
-			       atomic_read(&po->mapped));
+		if (atomic64_read(&po->mapped))
+			pr_err("packet_mmap: vma is busy: %lld\n",
+			       atomic64_read(&po->mapped));
 	}
 	mutex_unlock(&po->pg_vec_lock);
 
@@ -4606,7 +4606,7 @@ static int packet_mmap(struct file *file, struct socket *sock,
 		}
 	}
 
-	atomic_inc(&po->mapped);
+	atomic64_inc(&po->mapped);
 	vma->vm_ops = &packet_mmap_ops;
 	err = 0;
 
diff --git a/net/packet/internal.h b/net/packet/internal.h
index d29c94c45159..24acd0044a0d 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -122,7 +122,7 @@ struct packet_sock {
 	__be16			num;
 	struct packet_rollover	*rollover;
 	struct packet_mclist	*mclist;
-	atomic_t		mapped;
+	atomic64_t		mapped;
 	enum tpacket_versions	tp_version;
 	unsigned int		tp_hdrlen;
 	unsigned int		tp_reserve;
-- 
2.43.0