linux-kernel - [PATCH] carl9170: tx: fix an incorrect use of list iterator

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Date:   Sun, 27 Mar 2022 15:29:47 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     kvalo@...nel.org, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com
Cc:     linville@...driver.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, stable@...r.kernel.org
Subject: [PATCH] carl9170: tx: fix an incorrect use of list iterator

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 make 'cvif' NULL when
no entry found, to fix this bug.

Cc: stable@...r.kernel.org
Fixes: 1f1d9654e183c ("carl9170: refactor carl9170_update_beacon")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 drivers/net/wireless/ath/carl9170/tx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c
index 1b76f4434c06..2b8084121001 100644
--- a/drivers/net/wireless/ath/carl9170/tx.c
+++ b/drivers/net/wireless/ath/carl9170/tx.c
@@ -1558,6 +1558,9 @@ static struct carl9170_vif_info *carl9170_pick_beaconing_vif(struct ar9170 *ar)
 					goto out;
 			}
 		} while (ar->beacon_enabled && i--);
+
+		/* no entry found in list */
+		cvif = NULL;
 	}

 out:
-- 
2.17.1