[PATCH net-next v3 1/4] net: dm: check the boundary of skb drop reasons

[menglong8 . dong]

From: Menglong Dong <imagedong@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Reviewed-by: Hao Peng <flyingpeng@xxxxxxxxxxx>
Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
---
 net/core/drop_monitor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index b89e3e95bffc..41cac0e4834e 100644
--- 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;
-- 
2.36.1