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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, Jakub Kicinski <kuba@kernel.org>,
        Heiner Kallweit <hkallweit1@gmail.com>
Subject: [PATCH 4.19 093/101] r8169: fix potential skb double free in an error path
Date:   Tue, 17 Nov 2020 14:06:00 +0100
Message-Id: <20201117122117.666876711@linuxfoundation.org>
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From: Heiner Kallweit <hkallweit1@gmail.com>

[ Upstream commit cc6528bc9a0c901c83b8220a2e2617f3354d6dd9 ]

The caller of rtl8169_tso_csum_v2() frees the skb if false is returned.
eth_skb_pad() internally frees the skb on error what would result in a
double free. Therefore use __skb_put_padto() directly and instruct it
to not free the skb on error.

Fixes: b423e9ae49d7 ("r8169: fix offloaded tx checksum for small packets.")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/f7e68191-acff-9ded-4263-c016428a8762@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/realtek/r8169.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -6274,7 +6274,8 @@ static bool rtl8169_tso_csum_v2(struct r
 		opts[1] |= transport_offset << TCPHO_SHIFT;
 	} else {
 		if (unlikely(rtl_test_hw_pad_bug(tp, skb)))
-			return !eth_skb_pad(skb);
+			/* eth_skb_pad would free the skb on error */
+			return !__skb_put_padto(skb, ETH_ZLEN, false);
 	}
 
 	return true;