netdev - [PATCH RFC net] net/mlx5: Avoid NULL dereference in dest_is

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Message-Id: <20250618-mlx5-dest-v1-1-db983334259a@kernel.org>
Date: Wed, 18 Jun 2025 19:27:00 +0100
From: Simon Horman <horms@...nel.org>
To: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, 
 Tariq Toukan <tariqt@...dia.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Mark Bloch <markb@...lanox.com>, Paul Blakey <paulb@...lanox.com>, 
 netdev@...r.kernel.org, linux-rdma@...r.kernel.org, 
 Simon Horman <horms@...nel.org>
Subject: [PATCH RFC net] net/mlx5: Avoid NULL dereference in dest_is_valid

Elsewhere in dest_is_valid it is assumed that dest may be NULL.
But the line updated by this patch dereferences dest unconditionally.
This seems to be inconsistent.

Flagged by Smatch.
Compile tested only.

Fixes: ff189b435682 ("net/mlx5: Add ignore level support fwd to table rules")
Signed-off-by: Simon Horman <horms@...nel.org>
---
I am posting this as an RFC as I am not completely sure this change is
necessary. F.e. an invariant that I'm unaware of may preclude dest
from being NULL in this case.
---
 drivers/net/ethernet/mellanox/mlx5/core/fs_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
index a8046200d376..7eeab93a1aa9 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
@@ -2041,7 +2041,8 @@ static bool dest_is_valid(struct mlx5_flow_destination *dest,
 		    ft->type != FS_FT_NIC_TX)
 			return false;

-		if (dest->type == MLX5_FLOW_DESTINATION_TYPE_FLOW_TABLE &&
+		if (dest &&
+		    dest->type == MLX5_FLOW_DESTINATION_TYPE_FLOW_TABLE &&
 		    ft->type != dest->ft->type)
 			return false;
 	}