[PATCH v2] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[PATCH v2] 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")
---
v2: move allocation back into caller, as suggested by Saeed Mahameed

 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index af8c54d2e99c..7106006c792b 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -1266,13 +1266,10 @@ 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 void 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));
-
 	mlx5e_build_rq_param(priv, &cparam->rq);
 	mlx5e_build_sq_param(priv, &cparam->sq);
 	mlx5e_build_icosq_param(priv, &cparam->icosq, icosq_log_wq_sz);
@@ -1283,7 +1280,7 @@ static void mlx5e_build_channel_param(struct mlx5e_priv *priv,
 
 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;
@@ -1295,12 +1292,15 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)
 	priv->txq_to_sq_map = kcalloc(nch * priv->params.num_tc,
 				      sizeof(struct mlx5e_sq *), GFP_KERNEL);
 
-	if (!priv->channel || !priv->txq_to_sq_map)
+	cparam = kzalloc(sizeof(struct mlx5e_channel_param), GFP_KERNEL);
+
+	if (!priv->channel || !priv->txq_to_sq_map || !cparam)
 		goto err_free_txq_to_sq_map;
 
-	mlx5e_build_channel_param(priv, &cparam);
+	mlx5e_build_channel_param(priv, cparam);
+
 	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;
 	}
@@ -1311,6 +1311,7 @@ static int mlx5e_open_channels(struct mlx5e_priv *priv)
 			goto err_close_channels;
 	}
 
+	kfree(cparam);
 	return 0;
 
 err_close_channels:
@@ -1320,6 +1321,7 @@ err_close_channels:
 err_free_txq_to_sq_map:
 	kfree(priv->txq_to_sq_map);
 	kfree(priv->channel);
+	kfree(cparam);
 
 	return err;
 }
-- 
2.7.0

Re: [PATCH v2] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[Saeed Mahameed]

On Tue, Apr 26, 2016 at 6:52 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")

Acked-by: Saeed Mahameed <saeedm-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
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Re: [PATCH v2] net/mlx5e: avoid stack overflow in mlx5e_open_channels

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Tue, 26 Apr 2016 17:52:33 +0200

> 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")
> ---
> v2: move allocation back into caller, as suggested by Saeed Mahameed

Applied, thanks Arnd.