packet: avoid out of bounds read in round robin fanout

[android-x86/kernel.git] / net / packet / af_packet.c

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index b4dfdff..bfe5c69 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1266,16 +1266,6 @@ static void packet_sock_destruct(struct sock *sk)
        sk_refcnt_debug_dec(sk);
 }
 
-static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
-{
-       int x = atomic_read(&f->rr_cur) + 1;
-
-       if (x >= num)
-               x = 0;
-
-       return x;
-}
-
 static unsigned int fanout_demux_hash(struct packet_fanout *f,
                                      struct sk_buff *skb,
                                      unsigned int num)
@@ -1287,13 +1277,9 @@ static unsigned int fanout_demux_lb(struct packet_fanout *f,
                                    struct sk_buff *skb,
                                    unsigned int num)
 {
-       int cur, old;
+       unsigned int val = atomic_inc_return(&f->rr_cur);
 
-       cur = atomic_read(&f->rr_cur);
-       while ((old = atomic_cmpxchg(&f->rr_cur, cur,
-                                    fanout_rr_next(f, num))) != cur)
-               cur = old;
-       return cur;
+       return val % num;
 }
 
 static unsigned int fanout_demux_cpu(struct packet_fanout *f,