If 'idx' is 0, then 'idx2' is -1, and arrays 
will be accessed by a negative index. 

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Igor Artemiev <Igor.A.Artemiev@mcst.ru>
---
 net/mac80211/rx.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index e751cda5eef6..e686380434bd 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1868,10 +1868,13 @@ ieee80211_rx_get_bigtk(struct ieee80211_rx_data *rx, int idx)
 		key = rcu_dereference(rx->link_sta->gtk[idx]);
 	if (!key)
 		key = rcu_dereference(rx->link->gtk[idx]);
-	if (!key && rx->link_sta)
-		key = rcu_dereference(rx->link_sta->gtk[idx2]);
-	if (!key)
-		key = rcu_dereference(rx->link->gtk[idx2]);
+
+	if (idx2 >= 0) {
+		if (!key && rx->link_sta)
+			key = rcu_dereference(rx->link_sta->gtk[idx2]);
+		if (!key)
+			key = rcu_dereference(rx->link->gtk[idx2]);
+	}
 
 	return key;
 }
-- 
2.30.2

On Wed, 2023-10-04 at 17:37 +0300, Igor Artemiev wrote:
> If 'idx' is 0

And ... how exactly do you propose that is going to happen?

johannes

On 10/4/23 17:58, Johannes Berg wrote:
> And ... how exactly do you propose that is going to happen?

'conf.keyidx', the value that is passed to the function, can be 0. But I 
missed checking the second argument of the ieee80211_rx_get_bigtk() 
function before calling it. Sorry to bother you.

Thanks,
Igor