net: gtp: Fix Use-After-Free in gtp_dellink

Since call_rcu, which is called in the hlist_for_each_entry_rcu traversal
of gtp_dellink, is not part of the RCU read critical section, it
is possible that the RCU grace period will pass during the traversal and
the key will be free.

To prevent this, it should be changed to hlist_for_each_entry_safe.

Fixes: 94dc550a5062 ("gtp: fix an use-after-free in ipv4_pdp_find()")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index ba4704c2c640b860c55655607f8dd5cc044cfa3e..e62d6cbdf9bc6458064c7c0852fc23db095ae642 100644 (file)
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1098,11 +1098,12 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
 static void gtp_dellink(struct net_device *dev, struct list_head *head)
 {
        struct gtp_dev *gtp = netdev_priv(dev);
+       struct hlist_node *next;
        struct pdp_ctx *pctx;
        int i;
 
        for (i = 0; i < gtp->hash_size; i++)
-               hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid)
+               hlist_for_each_entry_safe(pctx, next, &gtp->tid_hash[i], hlist_tid)
                        pdp_context_delete(pctx);
 
        list_del_rcu(&gtp->list);