From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C3A136BCDA for ; Thu, 21 May 2026 20:46:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779396410; cv=none; b=P+jFGuMRRm7cCD/sxFswEZy+orurL3UjcpRI5usT/xH6BAtkUIHa31l7evwQUkNoo4kXSUbx1og6PZKcPrbF6vnrRN1+VV7G/eDeLMEH7zjNPvU3fSy2SYyAJ9agH5oei/Rb9WjhFUeQ4wiRheA5hc76MRPtPiUllIerBpNFF7w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779396410; c=relaxed/simple; bh=Hroq4/kCtxq0aHuQaOsF+Ycfj4RY/KmgOVmy+9IIpPQ=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=cRW+EO7NFQ8NezzWiLkSbJir47V1piv7Tn1fvQo+rNtrGd+MiwiKN5XUSW6dsXMkpfi5QAnB3v9muVxSwKQ09qCEdamoILSKPHBP3FkAuJggcKkwBM2/Zw5VPRcSMF3jKDshKVRANlW86HSXQ/sEFDgEn9kSL4yTOKhmW8H1W2A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fXJzpO4s; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fXJzpO4s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B19481F000E9; Thu, 21 May 2026 20:46:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779396408; bh=XCzF29he5XhGAdKJILoW3a0tRcnB+Pp2iNRpd+nn+u8=; h=Date:From:To:Cc:Subject:References; b=fXJzpO4sR3MVIp0fBhQoLS7MA7/zJNkV8or93HadmOQfwVDazknXa0XZuc83hywdz OKnINmLBGuVG+5XryNBoOKYavStFNpyup3XuLQ+PQ8VymRdrJg0p+PDjRuknp4B4Uf i5Qs+8A7D4bgHQzsjJnVbOfyQuG9qWwKreN2h+0IYXXRbJHUg6MFf3xoU4XHVSOIeJ dVPR40mV6WlxRt286PnTI5lxrP/fsBt/TzadmxNdk7VRN9GUcEJovuDfeOPs1XTDU3 AipZs0TqW25Mq2ICVQarXyI91n6C6VQfoGiQHFkWS0KqNqISXh7ewEwdHk+ZaNozo5 9HROa2aLi30yQ== Received: from rostedt by gandalf with local (Exim 4.99.2) (envelope-from ) id 1wQAIQ-00000005bnl-2wdT; Thu, 21 May 2026 16:47:10 -0400 Message-ID: <20260521204710.557408874@kernel.org> User-Agent: quilt/0.69 Date: Thu, 21 May 2026 16:45:28 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , David Carlier Subject: [for-linus][PATCH 1/2] tracing: Avoid NULL return from hist_field_name() on truncation References: <20260521204527.100913207@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: David Carlier 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 --- kernel/trace/trace_events_hist.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 0dbbf6cca9bc..eb2c2bc8bc3d 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1369,10 +1369,8 @@ static const char *hist_field_name(struct hist_field *field, len = snprintf(full_name, sizeof(full_name), fmt, field->system, field->event_name, field->name); - if (len >= sizeof(full_name)) - return NULL; - - field_name = full_name; + if (len < sizeof(full_name)) + field_name = full_name; } else field_name = field->name; } else if (field->flags & HIST_FIELD_FL_TIMESTAMP) -- 2.53.0