From: Edward Cree <ecree@solarflare.com>
Date: Tue, 18 Aug 2020 13:44:18 +0100
Subject: sfc: null out channel->rps_flow_id after freeing it
Patch-mainline: v5.9-rc2
Git-commit: 788f920a0f137baa4dbc1efdd5039c4a0a01b8d7
References: jsc#SLE-16683

If an ef100_net_open() fails, ef100_net_stop() may be called without
 channel->rps_flow_id having been written; thus it may hold the address
 freed by a previous ef100_net_stop()'s call to efx_remove_filters().
 This then causes a double-free when efx_remove_filters() is called
 again, leading to a panic.
To prevent this, after freeing it, overwrite it with NULL.

Fixes: a9dc3d5612ce ("sfc_ef100: RX filter table management and related gubbins")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/sfc/rx_common.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -849,6 +849,7 @@ void efx_remove_filters(struct efx_nic *
 	efx_for_each_channel(channel, efx) {
 		cancel_delayed_work_sync(&channel->filter_work);
 		kfree(channel->rps_flow_id);
+		channel->rps_flow_id = NULL;
 	}
 #endif
 	down_write(&efx->filter_sem);