net: convert sock.sk_wmem_alloc 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.

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>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/atm/mpc.c b/net/atm/mpc.c
index a190800572bd..680a4b9095a1 100644
--- a/net/atm/mpc.c
+++ b/net/atm/mpc.c
@@ -555,7 +555,7 @@ static int send_via_shortcut(struct sk_buff *skb, struct mpoa_client *mpc)
                                         sizeof(struct llc_snap_hdr));
         }
 
-        atomic_add(skb->truesize, &sk_atm(entry->shortcut)->sk_wmem_alloc);
+        refcount_add(skb->truesize, &sk_atm(entry->shortcut)->sk_wmem_alloc);
         ATM_SKB(skb)->atm_options = entry->shortcut->atm_options;
         entry->shortcut->send(entry->shortcut, skb);
         entry->packets_fwded++;
@@ -911,7 +911,7 @@ static int msg_from_mpoad(struct atm_vcc *vcc, struct sk_buff *skb)
 
         struct mpoa_client *mpc = find_mpc_by_vcc(vcc);
         struct k_message *mesg = (struct k_message *)skb->data;
-        atomic_sub(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc);
+        WARN_ON(refcount_sub_and_test(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc));
 
         if (mpc == NULL) {
                 pr_info("no mpc found\n");