net: dm: check the boundary of skb drop reasons

The 'reason' will be set to 'SKB_DROP_REASON_NOT_SPECIFIED' if it not
small that SKB_DROP_REASON_MAX in net_dm_packet_trace_kfree_skb_hit(),
but it can't avoid it to be 0, which is invalid and can cause NULL
pointer in drop_reasons.

Therefore, reset it to SKB_DROP_REASON_NOT_SPECIFIED when 'reason <= 0'.

Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index b89e3e95bffc0f50d477e86959f2bb42af9dce46..41cac0e4834e82fc33de1e369fb1e640bc7b7d59 100644 (file)
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -517,7 +517,7 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
        if (!nskb)
                return;
 
-       if ((unsigned int)reason >= SKB_DROP_REASON_MAX)
+       if (unlikely(reason >= SKB_DROP_REASON_MAX || reason <= 0))
                reason = SKB_DROP_REASON_NOT_SPECIFIED;
        cb = NET_DM_SKB_CB(nskb);
        cb->reason = reason;