[PATCH] ath: dfs_pattern_detector: Fix possible null-pointer dereference in channel_detector_create()

kzalloc() is used to allocate memory for cd->detectors, and if it fails,
channel_detector_exit() behind the label fail will be called:
  channel_detector_exit(dpd, cd);

In channel_detector_exit(), cd->detectors is dereferenced through:
  struct pri_detector *de = cd->detectors[i];

To fix this possible null-pointer dereference, check cd->detectors before 
the for loop to dereference cd->detectors. 

Reported-by: TOTE Robot <redacted>
Signed-off-by: Tuo Li <redacted>
---
 drivers/net/wireless/ath/dfs_pattern_detector.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/dfs_pattern_detector.c b/drivers/net/wireless/ath/dfs_pattern_detector.c
index 80390495ea25..75cb53a3ec15 100644
--- a/drivers/net/wireless/ath/dfs_pattern_detector.c
+++ b/drivers/net/wireless/ath/dfs_pattern_detector.c

@@ -183,10 +183,12 @@ static void channel_detector_exit(struct dfs_pattern_detector *dpd,
 	if (cd == NULL)
 		return;
 	list_del(&cd->head);
-	for (i = 0; i < dpd->num_radar_types; i++) {
-		struct pri_detector *de = cd->detectors[i];
-		if (de != NULL)
-			de->exit(de);
+	if (cd->detectors) {
+		for (i = 0; i < dpd->num_radar_types; i++) {
+			struct pri_detector *de = cd->detectors[i];
+			if (de != NULL)
+				de->exit(de);
+		}
 	}
 	kfree(cd->detectors);
 	kfree(cd);

-- 
2.25.1