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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, Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.9 320/757] mt76: fix a possible NULL pointer dereference in mt76_testmode_dump
Date:   Tue, 27 Oct 2020 14:49:30 +0100
Message-Id: <20201027135505.542793187@linuxfoundation.org>
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From: Lorenzo Bianconi <lorenzo@kernel.org>

[ Upstream commit ce8463a726a5669b200a1c2c17f95bc1394cc6bf ]

Fix a possible NULL pointer dereference in mt76_testmode_dump() since
nla_nest_start returns NULL in case of error

Fixes: f0efa8621550e ("mt76: add API for testmode support")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/mediatek/mt76/testmode.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/testmode.c b/drivers/net/wireless/mediatek/mt76/testmode.c
index 75bb02cdfdae4..5bd6ac1ba3b5b 100644
--- a/drivers/net/wireless/mediatek/mt76/testmode.c
+++ b/drivers/net/wireless/mediatek/mt76/testmode.c
@@ -442,9 +442,13 @@ int mt76_testmode_dump(struct ieee80211_hw *hw, struct sk_buff *msg,
 	mutex_lock(&dev->mutex);
 
 	if (tb[MT76_TM_ATTR_STATS]) {
+		err = -EINVAL;
+
 		a = nla_nest_start(msg, MT76_TM_ATTR_STATS);
-		err = mt76_testmode_dump_stats(dev, msg);
-		nla_nest_end(msg, a);
+		if (a) {
+			err = mt76_testmode_dump_stats(dev, msg);
+			nla_nest_end(msg, a);
+		}
 
 		goto out;
 	}
-- 
2.25.1