The field_var_str array was allocated separately via kcalloc() with its length already known at elt_data allocation time. Convert it to a flexible array member and fold the two allocations into a single kzalloc_flex(), reordering hist_trigger_elt_data_alloc() so n_str is computed and bounds-checked before the struct allocation.
hist_elt_data is only reached through tracing_map_elt::private_data (a void *), never embedded, so adding a FAM imposes no tail-position constraint on any enclosing struct. Added __counted_by for extra runtime analysis. Assisted-by: Claude:Opus-4.7 Signed-off-by: Rosen Penev <[email protected]> --- kernel/trace/trace_events_hist.c | 31 +++++++++++-------------------- 1 file changed, 11 insertions(+), 20 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index a64c76f6905f..1fd0899c606c 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -683,8 +683,8 @@ struct track_data { struct hist_elt_data { char *comm; u64 *var_ref_vals; - char **field_var_str; int n_field_var_str; + char *field_var_str[] __counted_by(n_field_var_str); }; struct snapshot_context { @@ -1629,8 +1629,6 @@ static void hist_elt_data_free(struct hist_elt_data *elt_data) for (i = 0; i < elt_data->n_field_var_str; i++) kfree(elt_data->field_var_str[i]); - kfree(elt_data->field_var_str); - kfree(elt_data->comm); kfree(elt_data); } @@ -1650,10 +1648,19 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) struct hist_field *hist_field; unsigned int i, n_str; - elt_data = kzalloc_obj(*elt_data); + BUILD_BUG_ON(STR_VAR_LEN_MAX & (sizeof(u64) - 1)); + + n_str = hist_data->n_field_var_str + hist_data->n_save_var_str + + hist_data->n_var_str; + if (n_str > SYNTH_FIELDS_MAX) + return -EINVAL; + + elt_data = kzalloc_flex(*elt_data, field_var_str, n_str); if (!elt_data) return -ENOMEM; + elt_data->n_field_var_str = n_str; + for_each_hist_field(i, hist_data) { hist_field = hist_data->fields[i]; @@ -1667,24 +1674,8 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) } } - n_str = hist_data->n_field_var_str + hist_data->n_save_var_str + - hist_data->n_var_str; - if (n_str > SYNTH_FIELDS_MAX) { - hist_elt_data_free(elt_data); - return -EINVAL; - } - - BUILD_BUG_ON(STR_VAR_LEN_MAX & (sizeof(u64) - 1)); - size = STR_VAR_LEN_MAX; - elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL); - if (!elt_data->field_var_str) { - hist_elt_data_free(elt_data); - return -EINVAL; - } - elt_data->n_field_var_str = n_str; - for (i = 0; i < n_str; i++) { elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL); if (!elt_data->field_var_str[i]) { -- 2.54.0
