netdev - [PATCH][next] sfc: fix dereference of table before it is null checked

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Message-Id: <20200512171355.221810-1-colin.king@canonical.com>
Date:   Tue, 12 May 2020 18:13:55 +0100
From:   Colin King <colin.king@...onical.com>
To:     Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
        Edward Cree <ecree@...arflare.com>,
        Martin Habets <mhabets@...arflare.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] sfc: fix dereference of table before it is null checked

From: Colin Ian King <colin.king@...onical.com>

Currently pointer table is being dereferenced on a null check of
table->must_restore_filters before it is being null checked, leading
to a potential null pointer dereference issue.  Fix this by null
checking table before dereferencing it when checking for a null
table->must_restore_filters.

Addresses-Coverity: ("Dereference before null check")
Fixes: e4fe938cff04 ("sfc: move 'must restore' flags out of ef10-specific nic_data")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/net/ethernet/sfc/mcdi_filters.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/sfc/mcdi_filters.c b/drivers/net/ethernet/sfc/mcdi_filters.c
index 88de95a8c08c..455a62814fb9 100644
--- a/drivers/net/ethernet/sfc/mcdi_filters.c
+++ b/drivers/net/ethernet/sfc/mcdi_filters.c
@@ -1369,10 +1369,7 @@ void efx_mcdi_filter_table_restore(struct efx_nic *efx)
 
 	WARN_ON(!rwsem_is_locked(&efx->filter_sem));
 
-	if (!table->must_restore_filters)
-		return;
-
-	if (!table)
+	if (!table || !table->must_restore_filters)
 		return;
 
 	down_write(&table->lock);
-- 
2.25.1