[PATCH 14/17] net: convert inet_frag_queue.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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.reshet...@intel.com>
Signed-off-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: David Windsor <dwind...@gmail.com>
---
 include/net/inet_frag.h  |  4 ++--
 net/ipv4/inet_fragment.c | 14 +++++++-------
 net/ipv4/ip_fragment.c   |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 5894730..5a334bf 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -50,7 +50,7 @@ struct inet_frag_queue {
        spinlock_t              lock;
        struct timer_list       timer;
        struct hlist_node       list;
-       atomic_t                refcnt;
+       refcount_t              refcnt;
        struct sk_buff          *fragments;
        struct sk_buff          *fragments_tail;
        ktime_t                 stamp;
@@ -129,7 +129,7 @@ void inet_frag_maybe_warn_overflow(struct inet_frag_queue 
*q,
 
 static inline void inet_frag_put(struct inet_frag_queue *q, struct inet_frags 
*f)
 {
-       if (atomic_dec_and_test(&q->refcnt))
+       if (refcount_dec_and_test(&q->refcnt))
                inet_frag_destroy(q, f);
 }
 
diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index b5e9317..96e95e8 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -276,11 +276,11 @@ static inline void fq_unlink(struct inet_frag_queue *fq, 
struct inet_frags *f)
 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 {
        if (del_timer(&fq->timer))
-               atomic_dec(&fq->refcnt);
+               refcount_dec(&fq->refcnt);
 
        if (!(fq->flags & INET_FRAG_COMPLETE)) {
                fq_unlink(fq, f);
-               atomic_dec(&fq->refcnt);
+               refcount_dec(&fq->refcnt);
        }
 }
 EXPORT_SYMBOL(inet_frag_kill);
@@ -329,7 +329,7 @@ static struct inet_frag_queue *inet_frag_intern(struct 
netns_frags *nf,
         */
        hlist_for_each_entry(qp, &hb->chain, list) {
                if (qp->net == nf && f->match(qp, arg)) {
-                       atomic_inc(&qp->refcnt);
+                       refcount_inc(&qp->refcnt);
                        spin_unlock(&hb->chain_lock);
                        qp_in->flags |= INET_FRAG_COMPLETE;
                        inet_frag_put(qp_in, f);
@@ -339,9 +339,9 @@ static struct inet_frag_queue *inet_frag_intern(struct 
netns_frags *nf,
 #endif
        qp = qp_in;
        if (!mod_timer(&qp->timer, jiffies + nf->timeout))
-               atomic_inc(&qp->refcnt);
+               refcount_inc(&qp->refcnt);
 
-       atomic_inc(&qp->refcnt);
+       refcount_inc(&qp->refcnt);
        hlist_add_head(&qp->list, &hb->chain);
 
        spin_unlock(&hb->chain_lock);
@@ -370,7 +370,7 @@ static struct inet_frag_queue *inet_frag_alloc(struct 
netns_frags *nf,
 
        setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
        spin_lock_init(&q->lock);
-       atomic_set(&q->refcnt, 1);
+       refcount_set(&q->refcnt, 1);
 
        return q;
 }
@@ -405,7 +405,7 @@ struct inet_frag_queue *inet_frag_find(struct netns_frags 
*nf,
        spin_lock(&hb->chain_lock);
        hlist_for_each_entry(q, &hb->chain, list) {
                if (q->net == nf && f->match(q, key)) {
-                       atomic_inc(&q->refcnt);
+                       refcount_inc(&q->refcnt);
                        spin_unlock(&hb->chain_lock);
                        return q;
                }
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index b3cdeec..9a8cfac 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -312,7 +312,7 @@ static int ip_frag_reinit(struct ipq *qp)
        unsigned int sum_truesize = 0;
 
        if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
-               atomic_inc(&qp->q.refcnt);
+               refcount_inc(&qp->q.refcnt);
                return -ETIMEDOUT;
        }
 
-- 
2.7.4