[PATCH] iwlegacy: 3945-rs: fix possible null-pointer dereferences in il3945_rs_get_rate()

[Tuo Li <islituo@gmail.com>]

In this function, il_sta is assigned to rs_sta, and rs_sta is dereferenced
at several points. If il_sta is NULL, this can lead to null-pointer
dereferences. To fix this issue, add an early check for il_sta and return
if it is NULL, consistent with the handling in il3945_rs_tx_status().

Signed-off-by: Tuo Li <islituo@gmail.com>
---
 drivers/net/wireless/intel/iwlegacy/3945-rs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlegacy/3945-rs.c b/drivers/net/wireless/intel/iwlegacy/3945-rs.c
index 1826c37c090c..c13268093a6e 100644
--- a/drivers/net/wireless/intel/iwlegacy/3945-rs.c
+++ b/drivers/net/wireless/intel/iwlegacy/3945-rs.c
@@ -626,8 +626,13 @@ il3945_rs_get_rate(void *il_r, struct ieee80211_sta *sta, void *il_sta,
 
 	D_RATE("enter\n");
 
+	if (!il_sta) {
+		D_RATE("leave: No STA il data available!\n");
+		return;
+	}
+
 	/* Treat uninitialized rate scaling data same as non-existing. */
-	if (rs_sta && !rs_sta->il) {
+	if (!rs_sta->il) {
 		D_RATE("Rate scaling information not initialized yet.\n");
 		il_sta = NULL;
 	}
-- 
2.43.0