[PATCH 4.19 178/287] carl9170: tx: fix an incorrect use of list iterator

[Greg Kroah-Hartman]

From: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>

commit 54a6f29522da3c914da30e50721dedf51046449a upstream.

If the previous list_for_each_entry_continue_rcu() don't exit early
(no goto hit inside the loop), the iterator 'cvif' after the loop
will be a bogus pointer to an invalid structure object containing
the HEAD (&ar->vif_list). As a result, the use of 'cvif' after that
will lead to a invalid memory access (i.e., 'cvif->id': the invalid
pointer dereference when return back to/after the callsite in the
carl9170_update_beacon()).

The original intention should have been to return the valid 'cvif'
when found in list, NULL otherwise. So just return NULL when no
entry found, to fix this bug.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 1f1d9654e183c ("carl9170: refactor carl9170_update_beacon")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>
Acked-by: Christian Lamparter <chunkeey@xxxxxxxxx>
Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220328122820.1004-1-xiam0nd.tong@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/carl9170/tx.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/wireless/ath/carl9170/tx.c
+++ b/drivers/net/wireless/ath/carl9170/tx.c
@@ -1554,6 +1554,9 @@ static struct carl9170_vif_info *carl917
 					goto out;
 			}
 		} while (ar->beacon_enabled && i--);
+
+		/* no entry found in list */
+		return NULL;
 	}
 
 out: