net: convert inet_peer.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 conversion requires overall +1 on the whole
refcounting scheme.

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/include/net/inetpeer.h b/include/net/inetpeer.h
index 235c7811a86a1df748d838c6b4fd453cea0cbf40..f2a215fc78e4686f597c4041796663a7a463e73f 100644 (file)
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -46,7 +46,7 @@ struct inet_peer {
                struct rcu_head     gc_rcu;
        };
        /*
-        * Once inet_peer is queued for deletion (refcnt == -1), following field
+        * Once inet_peer is queued for deletion (refcnt == 0), following field
         * is not available: rid
         * We can share memory with rcu_head to help keep inet_peer small.
         */
@@ -60,7 +60,7 @@ struct inet_peer {
 
        /* following fields might be frequently dirtied */
        __u32                   dtime;  /* the time of last use of not referenced entries */
-       atomic_t                refcnt;
+       refcount_t              refcnt;
 };
 
 struct inet_peer_base {

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 86fa4580954060b1798c7f3382d77cbec41e6ff7..c5a117cc66198ca0fe9d49e1c15f3c3110a0d634 100644 (file)
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -115,7 +115,7 @@ static void inetpeer_gc_worker(struct work_struct *work)
 
                n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
 
-               if (!atomic_read(&p->refcnt)) {
+               if (refcount_read(&p->refcnt) == 1) {
                        list_del(&p->gc_list);
                        kmem_cache_free(peer_cachep, p);
                }
@@ -202,10 +202,11 @@ static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
                int cmp = inetpeer_addr_cmp(daddr, &u->daddr);
                if (cmp == 0) {
                        /* Before taking a reference, check if this entry was
-                        * deleted (refcnt=-1)
+                        * deleted (refcnt=0)
                         */
-                       if (!atomic_add_unless(&u->refcnt, 1, -1))
+                       if (!refcount_inc_not_zero(&u->refcnt)) {
                                u = NULL;
+                       }
                        return u;
                }
                if (cmp == -1)
@@ -382,11 +383,10 @@ static int inet_peer_gc(struct inet_peer_base *base,
        while (stackptr > stack) {
                stackptr--;
                p = rcu_deref_locked(**stackptr, base);
-               if (atomic_read(&p->refcnt) == 0) {
+               if (refcount_read(&p->refcnt) == 1) {
                        smp_rmb();
                        delta = (__u32)jiffies - p->dtime;
-                       if (delta >= ttl &&
-                           atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
+                       if (delta >= ttl && refcount_dec_if_one(&p->refcnt)) {
                                p->gc_next = gchead;
                                gchead = p;
                        }
@@ -432,7 +432,7 @@ struct inet_peer *inet_getpeer(struct inet_peer_base *base,
 relookup:
        p = lookup(daddr, stack, base);
        if (p != peer_avl_empty) {
-               atomic_inc(&p->refcnt);
+               refcount_inc(&p->refcnt);
                write_sequnlock_bh(&base->lock);
                return p;
        }
@@ -444,7 +444,7 @@ struct inet_peer *inet_getpeer(struct inet_peer_base *base,
        p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
        if (p) {
                p->daddr = *daddr;
-               atomic_set(&p->refcnt, 1);
+               refcount_set(&p->refcnt, 2);
                atomic_set(&p->rid, 0);
                p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
                p->rate_tokens = 0;
@@ -468,7 +468,7 @@ void inet_putpeer(struct inet_peer *p)
 {
        p->dtime = (__u32)jiffies;
        smp_mb__before_atomic();
-       atomic_dec(&p->refcnt);
+       refcount_dec(&p->refcnt);
 }
 EXPORT_SYMBOL_GPL(inet_putpeer);