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 8312C4D9564 for ; Wed, 16 Sep 2026 18:37:05 +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=1789583842; cv=none; b=ZVT1D1w663DQf9FjTHZbzznanvBZinQeC//6GoTjO2E//ImwhRQKLf6+V1n6ADOsp+P6T2wYoH2ega27LWihT30oGFIw+wb72s/fY/lGDbKExrRY0f5wUO/ysA2aO28y9z+dupgO4y4nuZ3YjrfL8KN8tMlZDvQSkpC2fHjRYkg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789583842; c=relaxed/simple; bh=8+lIgI8YMgqp/20HlLIcIAClnpvAP+d1d76pzxAfUIA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=edux66RuGOKeBZaTBCWaIR1zHoMOjnDi/+y5fpkVTuRhFcwb6OS99LtMDaYHHLIzoQ/GadV+u6IF1ha1m4bEsWuiXARjJhBuCgUP0xa9d4UKYpLcst2TYp8re/lCi6tDKKxnPPkcQWaFCxxVqe5BUiEPpeqTQBiCS+7LUeQJck8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R3RjdtO7; 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="R3RjdtO7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE73D1F00899; Wed, 16 Sep 2026 18:36:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789583818; bh=C+HRoRmYjmV6D/I9E9T1Bxl8eI+z1wdtBHICeRF5L18=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=R3RjdtO7tysjyo1LHWMK8pWIwbpHrm0h4WjMLLhEqCDsfI+ICA5VCXpf6325sCr1K kOXGBWzuu/q7UjsCUFu7qsOi/ZE4tk3q6oY4ZxGPfwt4G/wBY3xPAVnDcupEx6unEe 13cZ4ABJlUxHvDm6cr6HWr8zVITkQ1CNY0/41TiAXp4HTlxAYNSWcaNDz8HNzPi/SM HeMdc90DSWzRWYpRwJR5qVuowzZJpLonmGOHiak8E0fKCXFrwwehFLIxJYR+2g1F/O UBNLQcMKyBHdZ4oYmN32vUbHYrlR0P3lRaydYlc1Amzw1wuz4qbSFkz+frVfMD+zdY 9rmIf8PoXkiAQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Donggeun Yoo , Steven Rostedt , Sasha Levin Subject: [PATCH 5.15.y 2/2] tracing: Free histogram var refs regardless of how often they are referenced Date: Wed, 16 Sep 2026 14:36:55 -0400 Message-ID: <20260916183655.1773427-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260916183655.1773427-1-sashal@kernel.org> References: <2026091621-debtor-hazelnut-dfc6@gregkh> <20260916183655.1773427-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Donggeun Yoo [ Upstream commit 4bddcb346a6cf4615ca77f69a589623b877ca267 ] 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: Sasha Levin --- kernel/trace/trace_events_hist.c | 16 +--------------- 1 file changed, 1 insertion(+), 15 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 9596bb513ad3a..b9641fecb8c5b 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -146,7 +146,6 @@ 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; @@ -1629,16 +1628,8 @@ static int contains_operator(char *str) 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); @@ -1685,8 +1676,6 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data, 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) @@ -1907,10 +1896,8 @@ static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data, 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) @@ -2771,7 +2758,6 @@ static struct hist_field *create_var(struct hist_trigger_data *hist_data, goto out; } - var->ref = 1; var->flags = HIST_FIELD_FL_VAR; var->var.idx = idx; var->var.hist_data = var->hist_data = hist_data; -- 2.53.0