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SubjectRe: [PATCH 3/5] net/mlx4: fix some error handling in mlx4_multi_func_init()
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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@rasmusvillemoes.dk>
> ---
> 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]);
> }
>

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