net: convert packet_fanout.sk_ref 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>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 643302b..e3beb28 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1739,7 +1739,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
                match->flags = flags;
                INIT_LIST_HEAD(&match->list);
                spin_lock_init(&match->lock);
-               atomic_set(&match->sk_ref, 0);
+               refcount_set(&match->sk_ref, 0);
                fanout_init_data(match);
                match->prot_hook.type = po->prot_hook.type;
                match->prot_hook.dev = po->prot_hook.dev;
@@ -1753,10 +1753,10 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
            match->prot_hook.type == po->prot_hook.type &&
            match->prot_hook.dev == po->prot_hook.dev) {
                err = -ENOSPC;
-               if (atomic_read(&match->sk_ref) < PACKET_FANOUT_MAX) {
+               if (refcount_read(&match->sk_ref) < PACKET_FANOUT_MAX) {
                        __dev_remove_pack(&po->prot_hook);
                        po->fanout = match;
-                       atomic_inc(&match->sk_ref);
+                       refcount_set(&match->sk_ref, refcount_read(&match->sk_ref) + 1);
                        __fanout_link(sk, po);
                        err = 0;
                }
@@ -1785,7 +1785,7 @@ static struct packet_fanout *fanout_release(struct sock *sk)
        if (f) {
                po->fanout = NULL;
 
-               if (atomic_dec_and_test(&f->sk_ref))
+               if (refcount_dec_and_test(&f->sk_ref))
                        list_del(&f->list);
                else
                        f = NULL;

diff --git a/net/packet/internal.h b/net/packet/internal.h
index 9ee4631..94d1d40 100644 (file)
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -1,6 +1,8 @@
 #ifndef __PACKET_INTERNAL_H__
 #define __PACKET_INTERNAL_H__
 
+#include <linux/refcount.h>
+
 struct packet_mclist {
        struct packet_mclist    *next;
        int                     ifindex;
@@ -86,7 +88,7 @@ struct packet_fanout {
        struct list_head        list;
        struct sock             *arr[PACKET_FANOUT_MAX];
        spinlock_t              lock;
-       atomic_t                sk_ref;
+       refcount_t              sk_ref;
        struct packet_type      prot_hook ____cacheline_aligned_in_smp;
 };