netdev - [PATCH net] sfc: detach from cb_page in efx_copy

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Message-ID: <d0c0595d-899b-0701-11cc-d9298c97df74@solarflare.com>
Date:   Mon, 9 Mar 2020 18:16:24 +0000
From:   Edward Cree <ecree@...arflare.com>
To:     <davem@...emloft.net>
CC:     <linux-net-drivers@...arflare.com>, <netdev@...r.kernel.org>
Subject: [PATCH net] sfc: detach from cb_page in efx_copy_channel()

It's a resource, not a parameter, so we can't copy it into the new
 channel's TX queues, otherwise aliasing will lead to resource-
 management bugs if the channel is subsequently torn down without
 being initialised.

Before the Fixes:-tagged commit there was a similar bug with
 tsoh_page, but I'm not sure it's worth doing another fix for such
 old kernels.

Fixes: e9117e5099ea ("sfc: Firmware-Assisted TSO version 2")
Suggested-by: Derek Shute <Derek.Shute@...atus.com>
Signed-off-by: Edward Cree <ecree@...arflare.com>
---
The Fixes: is in v4.10, so this will want to go to stable for
 4.14 and later.  Note that the recent refactoring has moved the
 code; in the stable trees efx_copy_channel() will be in efx.c
 rather than efx_channels.c.

 drivers/net/ethernet/sfc/efx_channels.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
index aeb5e8aa2f2a..73d4e39b5b16 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c
@@ -583,6 +583,7 @@ struct efx_channel *efx_copy_channel(const struct efx_channel *old_channel)
 		if (tx_queue->channel)
 			tx_queue->channel = channel;
 		tx_queue->buffer = NULL;
+		tx_queue->cb_page = NULL;
 		memset(&tx_queue->txd, 0, sizeof(tx_queue->txd));
 	}