Suspect that temporary buffer may not be big enough.
LTO enables more inlining and therefore more bounds checking.

[3511/3591] Linking target drivers/librte_net_mlx5.so.25.2

In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [76, 524236]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [84, 524244]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [92, 524252]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [100, 524260]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [108, 524268]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [116, 524276]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^
In function ‘mlx5dr_action_prepare_decap_l3_data’,
    inlined from ‘mlx5dr_action_handle_tunnel_l3_to_l2’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2151:3,
    inlined from ‘mlx5dr_action_create_reformat_hws’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2221:9,
    inlined from ‘mlx5dr_action_create_reformat’ at
../drivers/net/mlx5/hws/mlx5dr_action.c:2278:8:
../drivers/net/mlx5/hws/mlx5dr_action.c:3630:17: warning: writing 4 bytes into
a region of size 0 [-Wstringop-overflow=]
 3630 |                 memcpy(dst, e_src, MLX5DR_ACTION_INLINE_DATA_SIZE); /*
data */
      |                 ^
../drivers/net/mlx5/hws/mlx5dr_action.c: In function
‘mlx5dr_action_create_reformat’:
../drivers/net/mlx5/hws/mlx5dr_action.c:2131:17: note: at offset [124, 524284]
into destination object ‘mh_data’ of size 64
 2131 |         uint8_t mh_data[MLX5DR_ACTION_REFORMAT_DATA_SIZE] = {0};
      |                 ^