linux-kernel - [PATCH 3/3] net/mlx5e: Fix use of freed pointer

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Message-Id: <20200927113254.362480-3-alex.dewar90@gmail.com>
Date:   Sun, 27 Sep 2020 12:32:53 +0100
From:   Alex Dewar <alex.dewar90@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Alex Dewar <alex.dewar90@...il.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Roi Dayan <roid@...lanox.com>, Oz Shlomo <ozsh@...lanox.com>,
        Paul Blakey <paulb@...lanox.com>,
        Ariel Levkovich <lariel@...dia.com>,
        Eli Britstein <elibr@...lanox.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] net/mlx5e: Fix use of freed pointer

If the call to mlx5_fc_create() fails, then shared_counter will be freed
before its member, shared_counter->counter, is accessed to retrieve the
error code. Fix by using an intermediate variable.

Addresses-Coverity: CID 1497153: Memory - illegal accesses (USE_AFTER_FREE)
Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
index b5f8ed30047b..5851a1dfe6e4 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
@@ -738,6 +738,7 @@ mlx5_tc_ct_shared_counter_get(struct mlx5_tc_ct_priv *ct_priv,
 	struct mlx5_ct_shared_counter *shared_counter;
 	struct mlx5_core_dev *dev = ct_priv->dev;
 	struct mlx5_ct_entry *rev_entry;
+	struct mlx5_fc *counter;
 	__be16 tmp_port;
 
 	/* get the reversed tuple */
@@ -775,12 +776,13 @@ mlx5_tc_ct_shared_counter_get(struct mlx5_tc_ct_priv *ct_priv,
 	if (!shared_counter)
 		return ERR_PTR(-ENOMEM);
 
-	shared_counter->counter = mlx5_fc_create(dev, true);
-	if (IS_ERR(shared_counter->counter)) {
+	counter = mlx5_fc_create(dev, true);
+	if (IS_ERR(counter)) {
 		ct_dbg("Failed to create counter for ct entry");
 		kfree(shared_counter);
-		return ERR_PTR(PTR_ERR(shared_counter->counter));
+		return (struct mlx5_ct_shared_counter *)counter;
 	}
+	shared_counter->counter = counter;
 
 	refcount_set(&shared_counter->refcount, 1);
 	return shared_counter;
-- 
2.28.0