[PATCH net] net/mlx5: FW tracer, clamp firmware-reported num_string_db

[Tariq Toukan <tariqt@nvidia.com>]

From: Akiva Goldberger <agoldberger@nvidia.com>

mlx5_query_mtrc_caps() reads num_string_db from the MTRC capabilities
register and uses it directly as a loop bound to populate the fixed-size
base_address_out[STRINGS_DB_SECTIONS_NUM] and
size_out[STRINGS_DB_SECTIONS_NUM] arrays in the tracer's str_db
structure (STRINGS_DB_SECTIONS_NUM == 8).

The field is 4 bits wide, so firmware can report up to 15. A value
greater than STRINGS_DB_SECTIONS_NUM makes the loop write past the end
of those arrays, corrupting adjacent fields of the fw_tracer structure
on the kernel heap. Clamp the firmware-reported value before it is used.

Fixes: f53aaa31cce7 ("net/mlx5: FW tracer, implement tracer logic")
Signed-off-by: Akiva Goldberger <agoldberger@nvidia.com>
Reviewed-by: Shay Drori <shayd@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c b/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
index adcc73e2a5b3..404736c46adf 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
@@ -64,6 +64,13 @@ static int mlx5_query_mtrc_caps(struct mlx5_fw_tracer *tracer)
 	tracer->str_db.num_string_trace =
 			MLX5_GET(mtrc_cap, out, num_string_trace);
 	tracer->str_db.num_string_db = MLX5_GET(mtrc_cap, out, num_string_db);
+	if (tracer->str_db.num_string_db > STRINGS_DB_SECTIONS_NUM) {
+		mlx5_core_warn(dev,
+			       "FWTracer: Firmware reports num_string_db (%u) > (%u), clamping\n",
+			       tracer->str_db.num_string_db,
+			       STRINGS_DB_SECTIONS_NUM);
+		tracer->str_db.num_string_db = STRINGS_DB_SECTIONS_NUM;
+	}
 	tracer->owner = !!MLX5_GET(mtrc_cap, out, trace_owner);
 	tracer->str_db.loaded = false;
 

base-commit: 3f1f755366687d051174739fb99f7d560202f60b
-- 
2.44.0