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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiaomeng Tong <xiam0nd.tong@gmail.com>,
        Christian Lamparter <chunkeey@gmail.com>,
        Kalle Valo <quic_kvalo@quicinc.com>
Subject: [PATCH 4.9 101/167] carl9170: tx: fix an incorrect use of list iterator
Date:   Mon, 13 Jun 2022 12:09:35 +0200
Message-Id: <20220613094904.473609077@linuxfoundation.org>
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From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

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@vger.kernel.org
Fixes: 1f1d9654e183c ("carl9170: refactor carl9170_update_beacon")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Acked-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220328122820.1004-1-xiam0nd.tong@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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: