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 B96D33839A8; Thu, 17 Sep 2026 15:51:14 +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=1789660276; cv=none; b=BTUzzNSLtmzPq2KlrW0Fi+mPOXZ0LSJgoX/fag+9OldVDexdTUWEIHOtgbxaOBikLVDDn3x7OYbHjRtd597A7nuDlFfgBcnu7WnWSGF31mUod5bY55rgxZ22UYT6G0Ie5z8xyzYzYduXFt36QqWZ0TycfRXp5dNS2vxtUO89GIA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660276; c=relaxed/simple; bh=8Uj2s3ow8o3EEv4k//O1OfMIWkmw2p6bY6Am+4Z6Q9g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nkDa6bFZ59CejLs5okzbXLEdvuZu1ylL/FLIsEnDQ/hHA76109w4LOP0RDWSCUG+YPS9wwcvUMae3EzjyPufesbjyampb6CWiz0qEB35TWV4U4qPwl0tUcWGFsrFro7isDISoYsXjfIlUp+GN1cJjR8GeXZxHD8T/HTtwE6DywQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=S/KWIO3S; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="S/KWIO3S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB7A11F000FF; Thu, 17 Sep 2026 15:51:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660274; bh=t0J0ISgHd5+RodcLIb8WzS7JoZe3zAG7+OM9pPi8+0I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S/KWIO3Ssd4qGfLjuML5Gw/uj1eC59n0wK8kLZdDXTxpNNXxYTNAFjUOSYp73ejtK mgJmCiikbEVJvNMDxULe0NDWwm4kV5rRa5fcYmtnYvivfdmRel47XkLig6HAOLccek 3BEKcOmqDY/gMrh3HLq3J2JuinHPulrbmFWu2FYU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Donggeun Yoo , Steven Rostedt Subject: [PATCH 7.2 498/733] tracing: Free histogram var refs regardless of how often they are referenced Date: Thu, 17 Sep 2026 16:13:26 +0100 Message-ID: <20260917151404.494119341@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Donggeun Yoo commit 4bddcb346a6cf4615ca77f69a589623b877ca267 upstream. Using the same variable three or more times in one hist trigger leaks the variable reference and its strings when the trigger is removed. commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy var_refs") made a trigger's var_refs[] array the only owner of a var ref: destroy_hist_field() returns early for HIST_FIELD_FL_VAR_REF, so the field expressions never destroy one. One entry, freed once, no count needed. commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") then made repeated references share one object and added a count of them. Only the increment side exists, since those expressions still return early and never drop a reference, so __destroy_hist_field() sees how many references were created rather than how many are left. It frees when the decremented count is 0 or 1, so two references work and three or more leak. Sharing kept one array entry per object, and create_var_ref() searches and appends within a single trigger, so nothing outside it holds the object. Removing a trigger whose variables are still referenced is already refused by check_var_refs() with -EBUSY. Drop the count and free unconditionally. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260906124025.3550596-1-donggeunyoo.kernel@gmail.com Fixes: 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") Signed-off-by: Donggeun Yoo Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_hist.c | 16 +--------------- 1 file changed, 1 insertion(+), 15 deletions(-) --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -170,7 +170,6 @@ struct hist_field { struct hist_field *operands[HIST_FIELD_OPERANDS_MAX]; struct hist_trigger_data *hist_data; enum hist_field_fn fn_num; - unsigned int ref; unsigned int size; unsigned int offset; unsigned int is_signed; @@ -1906,16 +1905,8 @@ out: return field_op; } -static void get_hist_field(struct hist_field *hist_field) -{ - hist_field->ref++; -} - static void __destroy_hist_field(struct hist_field *hist_field) { - if (--hist_field->ref > 1) - return; - kfree(hist_field->var.name); kfree(hist_field->name); @@ -1962,8 +1953,6 @@ static struct hist_field *create_hist_fi if (!hist_field) return NULL; - hist_field->ref = 1; - hist_field->hist_data = hist_data; if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS) @@ -2218,10 +2207,8 @@ static struct hist_field *create_var_ref for (i = 0; i < hist_data->n_var_refs; i++) { ref_field = hist_data->var_refs[i]; if (ref_field->var.idx == var_field->var.idx && - ref_field->var.hist_data == var_field->hist_data) { - get_hist_field(ref_field); + ref_field->var.hist_data == var_field->hist_data) return ref_field; - } } /* Sanity check to avoid out-of-bound write on 'hist_data->var_refs' */ if (hist_data->n_var_refs >= TRACING_MAP_VARS_MAX) @@ -3265,7 +3252,6 @@ static struct hist_field *create_var(str goto out; } - var->ref = 1; var->flags = HIST_FIELD_FL_VAR; var->var.idx = idx; var->var.hist_data = var->hist_data = hist_data;