Re: [PATCH] net/mlx5e: allocate 'indirection_rqt' buffer dynamically

From: Arnd Bergmann <arnd@arndb.de>

Increasing the size of the indirection_rqt array from 128 to 256 bytes
pushed the stack usage of the mlx5e_hairpin_fill_rqt_rqns() function
over the warning limit when building with clang and CONFIG_KASAN:

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c:970:1: error: stack frame size of 1180 bytes in function 'mlx5e_tc_add_nic_flow' [-Werror,-Wframe-larger-than=]

Using dynamic allocation here is safe because the caller does the
same, and it reduces the stack usage of the function to just a few
bytes.

Fixes: 1dd55ba2fb70 ("net/mlx5e: Increase indirection RQ table size to 256")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
  drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 16 +++++++++++++---
  1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
index 0da69b98f38f..66f98618dc13 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -445,12 +445,16 @@ static void mlx5e_hairpin_destroy_transport(struct mlx5e_hairpin *hp)
  	mlx5_core_dealloc_transport_domain(hp->func_mdev, hp->tdn);
  }
  
-static void mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
+static int mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
  {
-	u32 indirection_rqt[MLX5E_INDIR_RQT_SIZE], rqn;
+	u32 *indirection_rqt, rqn;
  	struct mlx5e_priv *priv = hp->func_priv;
  	int i, ix, sz = MLX5E_INDIR_RQT_SIZE;
  
+	indirection_rqt = kzalloc(sz, GFP_KERNEL);
+	if (!indirection_rqt)
+		return -ENOMEM;
+
  	mlx5e_build_default_indir_rqt(indirection_rqt, sz,
  				      hp->num_channels);
  

@@ -462,6 +466,9 @@ static void mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
  		rqn = hp->pair->rqn[ix];
  		MLX5_SET(rqtc, rqtc, rq_num[i], rqn);
  	}
+
+	kfree(indirection_rqt);
+	return 0;
  }
  
  static int mlx5e_hairpin_create_indirect_rqt(struct mlx5e_hairpin *hp)

@@ -482,12 +489,15 @@ static int mlx5e_hairpin_create_indirect_rqt(struct mlx5e_hairpin *hp)
  	MLX5_SET(rqtc, rqtc, rqt_actual_size, sz);
  	MLX5_SET(rqtc, rqtc, rqt_max_size, sz);
  
-	mlx5e_hairpin_fill_rqt_rqns(hp, rqtc);
+	err = mlx5e_hairpin_fill_rqt_rqns(hp, rqtc);
+	if (err)
+		goto out;
  
  	err = mlx5_core_create_rqt(mdev, in, inlen, &hp->indir_rqt.rqtn);
  	if (!err)
  		hp->indir_rqt.enabled = true;
  
+out:
  	kvfree(in);
  	return err;
  }