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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, Michael Chan <michael.chan@broadcom.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.20 30/76] bnxt_en: Drop oversize TX packets to prevent errors.
Date:   Fri,  8 Mar 2019 13:49:42 +0100
Message-Id: <20190308124915.881118015@linuxfoundation.org>
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References: <20190308124914.789210760@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Chan <michael.chan@broadcom.com>

[ Upstream commit 2b3c6885386020b1b9d92d45e8349637e27d1f66 ]

There have been reports of oversize UDP packets being sent to the
driver to be transmitted, causing error conditions.  The issue is
likely caused by the dst of the SKB switching between 'lo' with
64K MTU and the hardware device with a smaller MTU.  Patches are
being proposed by Mahesh Bandewar <maheshb@google.com> to fix the
issue.

In the meantime, add a quick length check in the driver to prevent
the error.  The driver uses the TX packet size as index to look up an
array to setup the TX BD.  The array is large enough to support all MTU
sizes supported by the driver.  The oversize TX packet causes the
driver to index beyond the array and put garbage values into the
TX BD.  Add a simple check to prevent this.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -497,6 +497,12 @@ normal_tx:
 	}
 
 	length >>= 9;
+	if (unlikely(length >= ARRAY_SIZE(bnxt_lhint_arr))) {
+		dev_warn_ratelimited(&pdev->dev, "Dropped oversize %d bytes TX packet.\n",
+				     skb->len);
+		i = 0;
+		goto tx_dma_error;
+	}
 	flags |= bnxt_lhint_arr[length];
 	txbd->tx_bd_len_flags_type = cpu_to_le32(flags);