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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, Lv Yunlong <lyl2019@mail.ustc.edu.cn>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 235/244] net:nfc:digital: Fix a double free in digital_tg_recv_dep_req
Date:   Wed, 12 May 2021 16:50:06 +0200
Message-Id: <20210512144750.523890395@linuxfoundation.org>
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From: Lv Yunlong <lyl2019@mail.ustc.edu.cn>

[ Upstream commit 75258586793efc521e5dd52a5bf6c7a4cf7002be ]

In digital_tg_recv_dep_req, it calls nfc_tm_data_received(..,resp).
If nfc_tm_data_received() failed, the callee will free the resp via
kfree_skb() and return error. But in the exit branch, the resp
will be freed again.

My patch sets resp to NULL if nfc_tm_data_received() failed, to
avoid the double free.

Fixes: 1c7a4c24fbfd9 ("NFC Digital: Add target NFC-DEP support")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/nfc/digital_dep.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/nfc/digital_dep.c b/net/nfc/digital_dep.c
index 65aaa9d7c813..bcd4d74e8a82 100644
--- a/net/nfc/digital_dep.c
+++ b/net/nfc/digital_dep.c
@@ -1276,6 +1276,8 @@ static void digital_tg_recv_dep_req(struct nfc_digital_dev *ddev, void *arg,
 	}
 
 	rc = nfc_tm_data_received(ddev->nfc_dev, resp);
+	if (rc)
+		resp = NULL;
 
 exit:
 	kfree_skb(ddev->chaining_skb);
-- 
2.30.2