Re: [PATCH 3/5] net/mlx4: fix some error handling in mlx4_multi_func_init()

From: Yishai Hadas
Date: Wed Feb 10 2016 - 04:40:24 EST


On 2/9/2016 10:11 PM, Rasmus Villemoes wrote:
The while loop after err_slaves should use post-decrement; otherwise
we'll fail to do the kfrees for i==0, and will run into out-of-bounds
accesses if the setup above failed already at i==0.

The predecrement in the --port is ok, since ->vlan_filter is
(bizarrely) 1-indexed. But I'm changing 'if' to 'while' since it's a
bit ugly to rely on MLX4_MAX_PORTS being 2.

[I'm not sure why one even bothers populating the ->vlan_filter array:
mlx4.h isn't #included by anything outside
drivers/net/ethernet/mellanox/mlx4/, and "git grep -C2 -w vlan_filter
drivers/net/ethernet/mellanox/mlx4/" seems to suggest that the
vlan_filter elements aren't used at all.]

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx4/cmd.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cmd.c b/drivers/net/ethernet/mellanox/mlx4/cmd.c
index d48d5793407d..bfe8234abbba 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cmd.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cmd.c
@@ -2369,7 +2369,7 @@ int mlx4_multi_func_init(struct mlx4_dev *dev)
kzalloc(sizeof(struct mlx4_vlan_fltr),
GFP_KERNEL);
if (!s_state->vlan_filter[port]) {
- if (--port)
+ while (--port)

Prefer to leave as-is. There is no way that mlx4 will ever have more than 2 ports.

kfree(s_state->vlan_filter[port]);
goto err_slaves;
}
@@ -2429,7 +2429,7 @@ err_thread:
flush_workqueue(priv->mfunc.master.comm_wq);
destroy_workqueue(priv->mfunc.master.comm_wq);
err_slaves:
- while (--i) {
+ while (i--) {

This fix is wrong as it hits the case that i arrived the last value then below code will access to a non valid entry in the array.

The expected fix should be:
while (--i >= 0)

for (port = 1; port <= MLX4_MAX_PORTS; port++)
kfree(priv->mfunc.master.slave_state[i].vlan_filter[port]);
}