From a244c241593b5b38a08f0df2cb43c26574efbdcb Mon Sep 17 00:00:00 2001 From: Lee Jones Date: Tue, 13 Oct 2026 11:24:48 +0000 Subject: [PATCH] tracing/histograms: Reject non-stacktrace fields for synthetic stacktrace fields In check_synth_field(), when a synthetic event field is a stacktrace (field->is_stack) and the histogram field is not a "long[" stacktrace array, validation falls through to the generic size and signedness comparison. Because parse_synth_field() sets a stacktrace field's type to "__data_loc unsigned long[]", its size is sizeof(u64) and synth_field_signed() marks it as signed. Consequently, any 8-byte signed scalar histogram field passes the fallback check, and its scalar value is subsequently dereferenced as a kernel stacktrace pointer in get_field_size() and trace_stack(). Furthermore, checking strstr(hist_field->type, "long[") is insufficient because tracepoint fields defined with __bitmask() or __rel_bitmask() also have type "__data_loc unsigned long[]" or "__rel_loc unsigned long[]", whilst create_hist_field() treats them as 4-byte scalar values without HIST_FIELD_FL_STACKTRACE. Propagate HIST_FIELD_FL_STACKTRACE to variable references and field variables (whilst excluding variable aliases from per-element stacktrace capture), and reject any mismatch between HIST_FIELD_FL_STACKTRACE and field->is_stack in check_synth_field(). Cc: stable@vger.kernel.org Fixes: 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces") Link: https://patch.msgid.link/20261013112449.1006088-1-lee@kernel.org Signed-off-by: Lee Jones Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt --- kernel/trace/trace_events_hist.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 571a57e0f369..dcb5d7321095 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -2121,7 +2121,8 @@ static int init_var_ref(struct hist_field *ref_field, ref_field->size = var_field->size; ref_field->is_signed = var_field->is_signed; ref_field->flags |= var_field->flags & - (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS); + (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS | + HIST_FIELD_FL_STACKTRACE); if (system) { ref_field->system = kstrdup(system, GFP_KERNEL); @@ -3318,6 +3319,7 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data, ret = PTR_ERR(var); goto err; } + var->flags |= val->flags & HIST_FIELD_FL_STACKTRACE; field_var = kzalloc_obj(struct field_var); if (!field_var) { @@ -3946,7 +3948,10 @@ static int check_synth_field(struct synth_event *event, && field->is_dynamic) return 0; - if (strstr(hist_field->type, "long[") && field->is_stack) + if (!!(hist_field->flags & HIST_FIELD_FL_STACKTRACE) != field->is_stack) + return -EINVAL; + + if (field->is_stack) return 0; if (strcmp(field->type, hist_field->type) != 0) { @@ -4487,7 +4492,8 @@ static int create_var_field(struct hist_trigger_data *hist_data, if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME) update_var_execname(hist_data->fields[val_idx]); - if (!ret && hist_data->fields[val_idx]->flags & + if (!ret && !(hist_data->fields[val_idx]->flags & HIST_FIELD_FL_ALIAS) && + hist_data->fields[val_idx]->flags & (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE)) hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++; @@ -5228,7 +5234,8 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data, if (hist_field->flags & HIST_FIELD_FL_VAR) { var_idx = hist_field->var.idx; - if (hist_field->flags & + if (!(hist_field->flags & HIST_FIELD_FL_ALIAS) && + hist_field->flags & (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE)) { unsigned int str_start, var_str_idx, idx; char *str, *val_str;