[PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Arnd Bergmann]

struct mlx5e_channel_param is a large structure that is allocated
on the stack of mlx5e_open_channels, and with a recent change
it has grown beyond the warning size for the maximum stack
that a single function should use:

mellanox/mlx5/core/en_main.c: In function 'mlx5e_open_channels':
mellanox/mlx5/core/en_main.c:1325:1: error: the frame size of 1072 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

The function is already using dynamic allocation and is not in
a fast path, so the easiest workaround is to use another kzalloc
for allocating the channel parameters.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: d3c9bc2743dc ("net/mlx5e: Added ICO SQs")
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 22742e1fbcb9..2ec547a80886 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -1266,12 +1266,14 @@ static void mlx5e_build_icosq_param(struct mlx5e_priv *priv,
 	param->icosq = true;
 }
 
-static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
-				      struct mlx5e_channel_param *cparam)
+static struct mlx5e_channel_param *mlx5e_build_channel_param(struct mlx5e_priv *priv)
 {
+	struct mlx5e_channel_param *cparam;
 	u8 icosq_log_wq_sz = MLX5E_PARAMS_MINIMUM_LOG_SQ_SIZE;
 
-	memset(cparam, 0, sizeof(*cparam));
+	cparam = kzalloc(sizeof(struct mlx5e_channel_param), GFP_KERNEL);
+	if (!cparam)
+		return NULL;
 
 	mlx5e_build_rq_param(priv, &cparam->rq);
 	mlx5e_build_sq_param(priv, &cparam->sq);
@@ -1279,11 +1281,13 @@ static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
 	mlx5e_build_rx_cq_param(priv, &cparam->rx_cq);
 	mlx5e_build_tx_cq_param(priv, &cparam->tx_cq);
 	mlx5e_build_ico_cq_param(priv, &cparam->icosq_cq, icosq_log_wq_sz);
+
+	return cparam;
 }
 
 static int mlx5e_open_channels(struct mlx5e_priv *priv)
 {
-	struct mlx5e_channel_param cparam;
+	struct mlx5e_channel_param *cparam;
 	int nch = priv->params.num_channels;
 	int err = -ENOMEM;
 	int i;
@@ -1298,9 +1302,12 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)
 	if (!priv->channel || !priv->txq_to_sq_map)
 		goto err_free_txq_to_sq_map;
 
-	mlx5e_build_channel_param(priv, &cparam);
+	cparam = mlx5e_build_channel_param(priv);
+	if (!cparam)
+		goto err_free_txq_to_sq_map;
+
 	for (i = 0; i < nch; i++) {
-		err = mlx5e_open_channel(priv, i, &cparam, &priv->channel[i]);
+		err = mlx5e_open_channel(priv, i, cparam, &priv->channel[i]);
 		if (err)
 			goto err_close_channels;
 	}
@@ -1311,11 +1318,13 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)
 			goto err_close_channels;
 	}
 
+	kfree(cparam);
 	return 0;
 
 err_close_channels:
 	for (i--; i >= 0; i--)
 		mlx5e_close_channel(priv->channel[i]);
+	kfree(cparam);
 
 err_free_txq_to_sq_map:
 	kfree(priv->txq_to_sq_map);
-- 
2.7.0

Re: [PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Saeed Mahameed]

On Mon, Apr 25, 2016 at 4:15 PM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> struct mlx5e_channel_param is a large structure that is allocated
> on the stack of mlx5e_open_channels, and with a recent change
> it has grown beyond the warning size for the maximum stack
> that a single function should use:
>
> mellanox/mlx5/core/en_main.c: In function 'mlx5e_open_channels':
> mellanox/mlx5/core/en_main.c:1325:1: error: the frame size of 1072 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
>
> The function is already using dynamic allocation and is not in
> a fast path, so the easiest workaround is to use another kzalloc
> for allocating the channel parameters.
>
> Signed-off-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
> Fixes: d3c9bc2743dc ("net/mlx5e: Added ICO SQs")
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index 22742e1fbcb9..2ec547a80886 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -1266,12 +1266,14 @@ static void mlx5e_build_icosq_param(struct mlx5e_priv *priv,
>         param->icosq = true;
>  }
>
> -static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
> -                                     struct mlx5e_channel_param *cparam)
> +static struct mlx5e_channel_param *mlx5e_build_channel_param(struct mlx5e_priv *priv)

I prefer to keep the function prototype as before and move the dynamic
allocation to mlx5e_open_channels,
to keep alloc/free symmetric in mlx5e_open_channels.

>  {
> +       struct mlx5e_channel_param *cparam;
>         u8 icosq_log_wq_sz = MLX5E_PARAMS_MINIMUM_LOG_SQ_SIZE;
>
> -       memset(cparam, 0, sizeof(*cparam));
> +       cparam = kzalloc(sizeof(struct mlx5e_channel_param), GFP_KERNEL);
> +       if (!cparam)
> +               return NULL;
>
>         mlx5e_build_rq_param(priv, &cparam->rq);
>         mlx5e_build_sq_param(priv, &cparam->sq);
> @@ -1279,11 +1281,13 @@ static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
>         mlx5e_build_rx_cq_param(priv, &cparam->rx_cq);
>         mlx5e_build_tx_cq_param(priv, &cparam->tx_cq);
>         mlx5e_build_ico_cq_param(priv, &cparam->icosq_cq, icosq_log_wq_sz);
> +
> +       return cparam;
>  }
>
>  static int mlx5e_open_channels(struct mlx5e_priv *priv)
>  {
> -       struct mlx5e_channel_param cparam;
> +       struct mlx5e_channel_param *cparam;
>         int nch = priv->params.num_channels;
>         int err = -ENOMEM;
>         int i;
> @@ -1298,9 +1302,12 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)

You can do the allocation here,  then you can benefit from the next
allocation check to test the 3 allocations altogether.
i.e:
if (!cparam || !priv->channel || !priv->txq_to_sq_map)
           goto err_free_txq_to_sq_map;

>         if (!priv->channel || !priv->txq_to_sq_map)
>                 goto err_free_txq_to_sq_map;
>
> -       mlx5e_build_channel_param(priv, &cparam);
> +       cparam = mlx5e_build_channel_param(priv);
> +       if (!cparam)
> +               goto err_free_txq_to_sq_map;
> +
>         for (i = 0; i < nch; i++) {
> -               err = mlx5e_open_channel(priv, i, &cparam, &priv->channel[i]);
> +               err = mlx5e_open_channel(priv, i, cparam, &priv->channel[i]);
>                 if (err)
>                         goto err_close_channels;
>         }
> @@ -1311,11 +1318,13 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)
>                         goto err_close_channels;
>         }
>
> +       kfree(cparam);
>         return 0;
>
>  err_close_channels:
>         for (i--; i >= 0; i--)
>                 mlx5e_close_channel(priv->channel[i]);
> +       kfree(cparam);
>
>  err_free_txq_to_sq_map:
>         kfree(priv->txq_to_sq_map);
> --
> 2.7.0
>


Saeed.
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Re: [PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Arnd Bergmann]

On Tuesday 26 April 2016 16:48:33 Saeed Mahameed wrote:
> >  }
> >
> > -static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
> > -                                     struct mlx5e_channel_param *cparam)
> > +static struct mlx5e_channel_param *mlx5e_build_channel_param(struct mlx5e_priv *priv)
> 
> I prefer to keep the function prototype as before and move the dynamic
> allocation to mlx5e_open_channels,
> to keep alloc/free symmetric in mlx5e_open_channels.
> 
> 

Sure, do you want to just edit this when you forward the patch, or
do you need me to do it?

	Arnd
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Re: [PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Saeed Mahameed]

On Tue, Apr 26, 2016 at 4:53 PM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
>
> Sure, do you want to just edit this when you forward the patch, or
> do you need me to do it?
>

Well, I won't say no if you want to do it :)

Saeed
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Re: [PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Arnd Bergmann]

On Tuesday 26 April 2016 17:41:45 Saeed Mahameed wrote:
> On Tue, Apr 26, 2016 at 4:53 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > Sure, do you want to just edit this when you forward the patch, or
> > do you need me to do it?
> >
> 
> Well, I won't say no if you want to do it 
> 

All I want is to get rid of the patch in my queue. I guess it's
worth the 10 minute of work ;-)

v2 coming

	Arnd

Re: [PATCH] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Saeed Mahameed]

On Tue, Apr 26, 2016 at 6:49 PM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> On Tuesday 26 April 2016 17:41:45 Saeed Mahameed wrote:
>> On Tue, Apr 26, 2016 at 4:53 PM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
>> >
>> > Sure, do you want to just edit this when you forward the patch, or
>> > do you need me to do it?
>> >
>>
>> Well, I won't say no if you want to do it
>>
>
> All I want is to get rid of the patch in my queue. I guess it's
> worth the 10 minute of work ;-)
>
> v2 coming
>
>         Arnd

Thank you Arnd, Appreciated.
Saeed.
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