Re: [PATCH] mlx4: Fix chunk sg list overflow in mlx4_alloc_icm()

[sebastien dugue <sebastien.dugue-6ktuUTfB/bM@public.gmane.org>]

  Hi Roland,

On Wed, 05 May 2010 10:42:11 -0700
Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> wrote:

> good catch, applied.  Did this hit you in practice?  I guess it would
> take a big coherent ICM allocation, were you getting those?

  Yes, some customer got hit by this, which ended up corrupting memory.

> 
> Also what do you think of this independent cleanup on top of your patch?
> It handles the error case for allocation and then avoids having the
> common case inside a deeper nested block:

  No problem, it indeed makes the code more readable.

  Thanks,

  Sebastien.

> 
>  drivers/net/mlx4/icm.c |   37 +++++++++++++++++++------------------
>  1 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/mlx4/icm.c b/drivers/net/mlx4/icm.c
> index ef62f17..b07e4de 100644
> --- a/drivers/net/mlx4/icm.c
> +++ b/drivers/net/mlx4/icm.c
> @@ -163,29 +163,30 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
>  			ret = mlx4_alloc_icm_pages(&chunk->mem[chunk->npages],
>  						   cur_order, gfp_mask);
>  
> -		if (!ret) {
> -			++chunk->npages;
> -
> -			if (coherent)
> -				++chunk->nsg;
> -			else if (chunk->npages == MLX4_ICM_CHUNK_LEN) {
> -				chunk->nsg = pci_map_sg(dev->pdev, chunk->mem,
> -							chunk->npages,
> -							PCI_DMA_BIDIRECTIONAL);
> -
> -				if (chunk->nsg <= 0)
> -					goto fail;
> -			}
> +		if (ret) {
> +			if (--cur_order < 0)
> +				goto fail;
> +			else
> +				continue;
> +		}
>  
> -			if (chunk->npages == MLX4_ICM_CHUNK_LEN)
> -				chunk = NULL;
> +		++chunk->npages;
>  
> -			npages -= 1 << cur_order;
> -		} else {
> -			--cur_order;
> -			if (cur_order < 0)
> +		if (coherent)
> +			++chunk->nsg;
> +		else if (chunk->npages == MLX4_ICM_CHUNK_LEN) {
> +			chunk->nsg = pci_map_sg(dev->pdev, chunk->mem,
> +						chunk->npages,
> +						PCI_DMA_BIDIRECTIONAL);
> +
> +			if (chunk->nsg <= 0)
>  				goto fail;
>  		}
> +
> +		if (chunk->npages == MLX4_ICM_CHUNK_LEN)
> +			chunk = NULL;
> +
> +		npages -= 1 << cur_order;
>  	}
>  
>  	if (!coherent && chunk) {
> 
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