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Commit 1cc9a98b authored by Reshetova, Elena's avatar Reshetova, Elena Committed by David S. Miller
Browse files

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: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 574a6020

include/net/inetpeer.h

+2 −2
Original line number Diff line number Diff line
@@ -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 {

net/ipv4/inetpeer.c

+9 −9
Original line number Diff line number Diff line
@@ -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);