From 74c4c79d8c48e0389c6fa51732407195583f1a2c Mon Sep 17 00:00:00 2001 From: David Carlier Date: Fri, 8 May 2026 20:57:47 +0100 Subject: [PATCH] tracing: Avoid NULL return from hist_field_name() on truncation ANBZ: #40753 commit e3f5d42cdc2f167719564693675f1eead81378ea stable. commit 576ec047d20b368b43c4d5db98c4f2e0f3c101ec upstream. hist_field_name() returns "" everywhere except the fully-qualified VAR_REF/EXPR case, where snprintf() truncation returns NULL early and bypasses the bottom NULL->"" guard. Callers don't expect NULL: strcat(expr, hist_field_name(field, 0)) at trace_events_hist.c:1758 and the strcmp() in the sort-key match loop at :4804 both deref it. system and event_name are bounded by MAX_EVENT_NAME_LEN, but the field name on a VAR_REF is kstrdup'd from a histogram variable name parsed out of the trigger string and has no length cap, so a long enough var name in a fully qualified reference can reach the truncation path. Keep the length check but leave field_name as "" on overflow. Link: https://patch.msgid.link/20260508195747.25492-1-devnexen@gmail.com Fixes: 5ec1d1e97de1 ("tracing: Rebuild full_name on each hist_field_name() call") Signed-off-by: David Carlier Signed-off-by: Steven Rostedt Signed-off-by: Sasha Levin [backport-note] PatchPilot-Conflict-Type: context_drift PatchPilot-Conflict-Files: kernel/trace/trace_events_hist.c PatchPilot-Resolution: kernel/trace/trace_events_hist.c: Take upstream snprintf+truncation-check version for hist_field_name [Fixes conflicts by PatchPilot] Fixes: CVE-2026-64028 Assisted-by: PatchPilot Signed-off-by: Yuanhe Shu --- kernel/trace/trace_events_hist.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 473f014eb56c..8c379abf5a89 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1101,13 +1101,13 @@ static const char *hist_field_name(struct hist_field *field, field->flags & HIST_FIELD_FL_VAR_REF) { if (field->system) { static char full_name[MAX_FILTER_STR_VAL]; + int len; - strcat(full_name, field->system); - strcat(full_name, "."); - strcat(full_name, field->event_name); - strcat(full_name, "."); - strcat(full_name, field->name); - field_name = full_name; + len = snprintf(full_name, sizeof(full_name), "%s.%s.%s", + field->system, field->event_name, + field->name); + if (len < sizeof(full_name)) + field_name = full_name; } else field_name = field->name; } else if (field->flags & HIST_FIELD_FL_TIMESTAMP) -- Gitee