Re: [PATCH] net/mlx4_en: fix off by one in error handling

On Wed, 14 Sep 2016, Tariq Toukan wrote:

On 14/09/2016 4:53 PM, Sebastian Ott wrote:

quoted

On Wed, 14 Sep 2016, Tariq Toukan wrote:

quoted

On 14/09/2016 2:09 PM, Sebastian Ott wrote:

quoted

If an error occurs in mlx4_init_eq_table the index used in the
err_out_unmap label is one too big which results in a panic in
mlx4_free_eq. This patch fixes the index in the error path.

You are right, but your change below does not cover all cases.
The full solution looks like this:

@@ -1260,7 +1260,7 @@ int mlx4_init_eq_table(struct mlx4_dev *dev)
                                              eq);
                 }
                 if (err)
-                       goto err_out_unmap;
+                       goto err_out_unmap_excluded;

In this case a call to mlx4_create_eq failed. Do you really have to call
mlx4_free_eq for this index again?

We agree on this part, that's why here we should goto the _excluded_ label.
For all other parts, we should not exclude the eq in the highest index, and
thus we goto the _non_excluded_ label.

But that's exactly what the original patch does. If the failure is within
the for loop at index i, we do the cleanup starting at index i-1. If the
failure is after the for loop then i == dev->caps.num_comp_vectors + 1
and we do the cleanup starting at index i == dev->caps.num_comp_vectors.

In the latter case your patch would have an out of bounds array access.

Regards,
Sebastian