[dpdk-dev] [PATCH] lib/librte_power: fix using variables before validity check

["Min Hu (Connor)" <humin29@huawei.com>]

From: HongBo Zheng <zhenghongbo3@huawei.com>

In function power_guest_channel_read_msg, 'lcore_id' is used before
validity check, which may cause buffer 'global_fds' accessed by index
'lcore_id' overflow.

This patch moves the validity check of 'lcore_id' before the 'lcore_id'
being used for the first time.

Fixes: 9dc843eb273b ("power: extend guest channel API for reading")
Cc: stable@dpdk.org

Signed-off-by: HongBo Zheng <zhenghongbo3@huawei.com>
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
---
 lib/power/guest_channel.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/power/guest_channel.c b/lib/power/guest_channel.c
index 2f7507a..d3de3f1 100644
--- a/lib/power/guest_channel.c
+++ b/lib/power/guest_channel.c
@@ -166,6 +166,12 @@ int power_guest_channel_read_msg(void *pkt,
 	if (pkt_len == 0 || pkt == NULL)
 		return -1;
 
+	if (lcore_id >= RTE_MAX_LCORE) {
+		RTE_LOG(ERR, GUEST_CHANNEL, "Channel(%u) is out of range 0...%d\n",
+				lcore_id, RTE_MAX_LCORE-1);
+		return -1;
+	}
+
 	fds.fd = global_fds[lcore_id];
 	fds.events = POLLIN;
 
@@ -179,12 +185,6 @@ int power_guest_channel_read_msg(void *pkt,
 		return -1;
 	}
 
-	if (lcore_id >= RTE_MAX_LCORE) {
-		RTE_LOG(ERR, GUEST_CHANNEL, "Channel(%u) is out of range 0...%d\n",
-				lcore_id, RTE_MAX_LCORE-1);
-		return -1;
-	}
-
 	if (global_fds[lcore_id] < 0) {
 		RTE_LOG(ERR, GUEST_CHANNEL, "Channel is not connected\n");
 		return -1;
-- 
2.7.4