[bug report] net/mlx5: Add direct rule fs_cmd implementation

Dan Carpenter
2022-05-11T13:57:45Z

[ I was reviewing old use after free warnings and stumbled across this
one which still needs fixing - dan ]

Hello Maor Gottlieb,

The patch 6a48faeeca10: "net/mlx5: Add direct rule fs_cmd
implementation" from Aug 20, 2019, leads to the following Smatch
static checker warning:

drivers/net/ethernet/mellanox/mlx5/core/steering/fs_dr.c:53 set_miss_action()
warn: 'action' was already freed.

drivers/net/ethernet/mellanox/mlx5/core/steering/fs_dr.c
28 static int set_miss_action(struct mlx5_flow_root_namespace *ns,
29 struct mlx5_flow_table *ft,
30 struct mlx5_flow_table *next_ft)
31 {
32 struct mlx5dr_action *old_miss_action;
33 struct mlx5dr_action *action = NULL;
34 struct mlx5dr_table *next_tbl;
35 int err;
36
37 next_tbl = next_ft ? next_ft->fs_dr_table.dr_table : NULL;
38 if (next_tbl) {
39 action = mlx5dr_action_create_dest_table(next_tbl);
40 if (!action)
41 return -EINVAL;
42 }
43 old_miss_action = ft->fs_dr_table.miss_action;
44 err = mlx5dr_table_set_miss_action(ft->fs_dr_table.dr_table, action);
45 if (err && action) {
46 err = mlx5dr_action_destroy(action);
47 if (err) {
48 action = NULL;
49 mlx5_core_err(ns->dev, "Failed to destroy action (%d)\n",
50 err);
51 }

If "err" is zero then "action" is freed.

52 }
--> 53 ft->fs_dr_table.miss_action = action;
^^^^^^
Use after free.

54 if (old_miss_action) {
55 err = mlx5dr_action_destroy(old_miss_action);
56 if (err)
57 mlx5_core_err(ns->dev, "Failed to destroy action (%d)\n",
58 err);
59 }
60
61 return err;
62 }

regards,
dan carpenter