[PATCH 5.10 53/67] net/mlx5e: Fix nullptr in mlx5e_hairpin_get_mdev()

Greg Kroah-Hartman
2021-08-02T14:02:46Z

From: Dima Chumak <dchumak@nvidia.com>

[ Upstream commit b1c2f6312c5005c928a72e668bf305a589d828d4 ]

The result of __dev_get_by_index() is not checked for NULL and then gets
dereferenced immediately.

Also, __dev_get_by_index() must be called while holding either RTNL lock
or @dev_base_lock, which isn't satisfied by mlx5e_hairpin_get_mdev() or
its callers. This makes the underlying hlist_for_each_entry() loop not
safe, and can have adverse effects in itself.

Fix by using dev_get_by_index() and handling nullptr return value when
ifindex device is not found. Update mlx5e_hairpin_get_mdev() callers to
check for possible PTR_ERR() result.

Fixes: 77ab67b7f0f9 ("net/mlx5e: Basic setup of hairpin object")
Addresses-Coverity: ("Dereference null return value")
Signed-off-by: Dima Chumak <dchumak@nvidia.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../net/ethernet/mellanox/mlx5/core/en_tc.c | 33 +++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
index 59837af959d0..1ad1692a5b2d 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
@@ -481,12 +481,32 @@ static void mlx5e_detach_mod_hdr(struct mlx5e_priv *priv,
static
struct mlx5_core_dev *mlx5e_hairpin_get_mdev(struct net *net, int ifindex)
{
+ struct mlx5_core_dev *mdev;
struct net_device *netdev;
struct mlx5e_priv *priv;

- netdev = __dev_get_by_index(net, ifindex);
+ netdev = dev_get_by_index(net, ifindex);
+ if (!netdev)
+ return ERR_PTR(-ENODEV);
+
priv = netdev_priv(netdev);
- return priv->mdev;
+ mdev = priv->mdev;
+ dev_put(netdev);
+
+ /* Mirred tc action holds a refcount on the ifindex net_device (see
+ * net/sched/act_mirred.c:tcf_mirred_get_dev). So, it's okay to continue using mdev
+ * after dev_put(netdev), while we're in the context of adding a tc flow.
+ *
+ * The mdev pointer corresponds to the peer/out net_device of a hairpin. It is then
+ * stored in a hairpin object, which exists until all flows, that refer to it, get
+ * removed.
+ *
+ * On the other hand, after a hairpin object has been created, the peer net_device may
+ * be removed/unbound while there are still some hairpin flows that are using it. This
+ * case is handled by mlx5e_tc_hairpin_update_dead_peer, which is hooked to
+ * NETDEV_UNREGISTER event of the peer net_device.
+ */
+ return mdev;
}

static int mlx5e_hairpin_create_transport(struct mlx5e_hairpin *hp)
@@ -685,6 +705,10 @@ mlx5e_hairpin_create(struct mlx5e_priv *priv, struct mlx5_hairpin_params *params

func_mdev = priv->mdev;
peer_mdev = mlx5e_hairpin_get_mdev(dev_net(priv->netdev), peer_ifindex);
+ if (IS_ERR(peer_mdev)) {
+ err = PTR_ERR(peer_mdev);
+ goto create_pair_err;
+ }

pair = mlx5_core_hairpin_create(func_mdev, peer_mdev, params);
if (IS_ERR(pair)) {
@@ -823,6 +847,11 @@ static int mlx5e_hairpin_flow_add(struct mlx5e_priv *priv,
int err;

peer_mdev = mlx5e_hairpin_get_mdev(dev_net(priv->netdev), peer_ifindex);
+ if (IS_ERR(peer_mdev)) {
+ NL_SET_ERR_MSG_MOD(extack, "invalid ifindex of mirred device");
+ return PTR_ERR(peer_mdev);
+ }
+
if (!MLX5_CAP_GEN(priv->mdev, hairpin) || !MLX5_CAP_GEN(peer_mdev, hairpin)) {
NL_SET_ERR_MSG_MOD(extack, "hairpin is not supported");
return -EOPNOTSUPP;
--
2.30.2