net: convert sk_buff.users 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, 4 insertions, 4 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f75897a33fa4..45dc6620dd74 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -176,7 +176,7 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
         memset(skb, 0, offsetof(struct sk_buff, tail));
         skb->head = NULL;
         skb->truesize = sizeof(struct sk_buff);
-        atomic_set(&skb->users, 1);
+        refcount_set(&skb->users, 1);
 
         skb->mac_header = (typeof(skb->mac_header))~0U;
 out:
@@ -247,7 +247,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
         /* Account for allocated memory : skb + skb->head */
         skb->truesize = SKB_TRUESIZE(size);
         skb->pfmemalloc = pfmemalloc;
-        atomic_set(&skb->users, 1);
+        refcount_set(&skb->users, 1);
         skb->head = data;
         skb->data = data;
         skb_reset_tail_pointer(skb);
@@ -314,7 +314,7 @@ struct sk_buff *__build_skb(void *data, unsigned int frag_size)
 
         memset(skb, 0, offsetof(struct sk_buff, tail));
         skb->truesize = SKB_TRUESIZE(size);
-        atomic_set(&skb->users, 1);
+        refcount_set(&skb->users, 1);
         skb->head = data;
         skb->data = data;
         skb_reset_tail_pointer(skb);
@@ -915,7 +915,7 @@ static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
         C(head_frag);
         C(data);
         C(truesize);
-        atomic_set(&n->users, 1);
+        refcount_set(&n->users, 1);
 
         atomic_inc(&(skb_shinfo(skb)->dataref));
         skb->cloned = 1;