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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, Stephane Graber <stgraber@ubuntu.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.15 21/37] drivers: net: xgene: Fix regression in CRC stripping
Date:   Fri, 25 Mar 2022 16:14:22 +0100
Message-Id: <20220325150420.540161348@linuxfoundation.org>
In-Reply-To: <20220325150419.931802116@linuxfoundation.org>
References: <20220325150419.931802116@linuxfoundation.org>
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From: Stephane Graber <stgraber@ubuntu.com>

commit e9e6faeafaa00da1851bcf47912b0f1acae666b4 upstream.

All packets on ingress (except for jumbo) are terminated with a 4-bytes
CRC checksum. It's the responsability of the driver to strip those 4
bytes. Unfortunately a change dating back to March 2017 re-shuffled some
code and made the CRC stripping code effectively dead.

This change re-orders that part a bit such that the datalen is
immediately altered if needed.

Fixes: 4902a92270fb ("drivers: net: xgene: Add workaround for errata 10GE_8/ENET_11")
Cc: stable@vger.kernel.org
Signed-off-by: Stephane Graber <stgraber@ubuntu.com>
Tested-by: Stephane Graber <stgraber@ubuntu.com>
Link: https://lore.kernel.org/r/20220322224205.752795-1-stgraber@ubuntu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/apm/xgene/xgene_enet_main.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -696,6 +696,12 @@ static int xgene_enet_rx_frame(struct xg
 	buf_pool->rx_skb[skb_index] = NULL;
 
 	datalen = xgene_enet_get_data_len(le64_to_cpu(raw_desc->m1));
+
+	/* strip off CRC as HW isn't doing this */
+	nv = GET_VAL(NV, le64_to_cpu(raw_desc->m0));
+	if (!nv)
+		datalen -= 4;
+
 	skb_put(skb, datalen);
 	prefetch(skb->data - NET_IP_ALIGN);
 	skb->protocol = eth_type_trans(skb, ndev);
@@ -717,12 +723,8 @@ static int xgene_enet_rx_frame(struct xg
 		}
 	}
 
-	nv = GET_VAL(NV, le64_to_cpu(raw_desc->m0));
-	if (!nv) {
-		/* strip off CRC as HW isn't doing this */
-		datalen -= 4;
+	if (!nv)
 		goto skip_jumbo;
-	}
 
 	slots = page_pool->slots - 1;
 	head = page_pool->head;