From nobody Thu Sep 19 23:12:37 2024 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) (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 ADD457D08D; Wed, 10 Jul 2024 09:20:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=60.244.123.138 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720603215; cv=none; b=HXw3zRdvkd7WoJ35O10GuRuIDmjx9v5kB8r2qpaiVzVvP0709xUCOpzuLCwa6mqHPNszTYLxC1O8/fQVw7qhViNv5B+FWJyqXi1nQDdZ83Hm5F1jvI3eb8MijGuhKuWS62wGfI9lF6FMlXB+HMk3aC4Be3bT6TVVhE8ZoEClFpY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720603215; c=relaxed/simple; bh=iiJTusJ4u14LeGpn7VxH39f7OV4SKz8UFp4fmuGIOSQ=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=uYR0T0Vp8kqVO7KNkpIiXc235c79cCfzU0xvptriN2Zb4VQx+MIjk4EbNZJsidUSDwjDcuZEuqCHzar2gGNAxJFneRSjKWB9Bj7+s5pY3+6e7aDqe2J9V0O+fUQhblbudiJ7ldOaqh1fhfVFInO3aWtf9Wm9KIzIBIKOzRMqYSU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com; spf=pass smtp.mailfrom=mediatek.com; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b=O/cGqZpr; arc=none smtp.client-ip=60.244.123.138 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mediatek.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="O/cGqZpr" X-UUID: 98dae7a03e9d11efb5b96b43b535fdb4-20240710 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=gwqM7M4CejLnrb6PXGa1wK3vz+TNRJWDRKuQxwjYyBM=; b=O/cGqZprTM4DrwyH+t66lCfKfaN7DGQhoz6Bq+iW93A9QHfNoJw+GyQGOzTxK33OHV5st2TxMm0hfiWAcIAx7wwOJF5RCImiEg65uODG8mA1LHDAr18aQBF4opE5msePrliJjOAuUS2Wx6eYNjQLH7KSNIPaeIr7WI0iSRzrg4k=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.40,REQID:8a4b6c98-70e6-4727-80d7-ff4540456c3e,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:ba885a6,CLOUDID:6e152dd5-0d68-4615-a20f-01d7bd41f0bb,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:11|1,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES :1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 0,NGT X-CID-BAS: 0,NGT,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_ULN X-UUID: 98dae7a03e9d11efb5b96b43b535fdb4-20240710 Received: from mtkmbs14n2.mediatek.inc [(172.21.101.76)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1549598604; Wed, 10 Jul 2024 17:20:06 +0800 Received: from mtkmbs13n1.mediatek.inc (172.21.101.193) by MTKMBS09N2.mediatek.inc (172.21.101.94) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Wed, 10 Jul 2024 02:20:06 -0700 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs13n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1118.26 via Frontend Transport; Wed, 10 Jul 2024 17:20:06 +0800 From: Tze-nan Wu To: CC: , , , , Tze-nan Wu , Mathieu Desnoyers , , , , Subject: [PATCH] tracing: Fix overflow in get_free_elt() Date: Wed, 10 Jul 2024 17:19:05 +0800 Message-ID: <20240710091908.7030-1-Tze-nan.Wu@mediatek.com> X-Mailer: git-send-email 2.18.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" "tracing_map->next_elt" in get_free_elt() is at risk of overflowing. Once it overflows, new elements can still be inserted into the tracing_map even though the maximum number of elements (`max_elts`) has been reached. Continuing to insert elements after the overflow could result in the tracing_map containing "tracing_map->max_size" elements, leaving no empty entries. If any attempt is made to insert an element into a full tracing_map using `__tracing_map_insert()`, it will cause an infinite loop with preemption disabled, leading to a CPU hang problem. Fix this by preventing any further increments to "tracing_map->next_elt" once it reaches "tracing_map->max_elt". Co-developed-by: Cheng-Jui Wang Signed-off-by: Cheng-Jui Wang Signed-off-by: Tze-nan Wu --- kernel/trace/tracing_map.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c index a4dcf0f24352..3a56e7c8aa4f 100644 --- a/kernel/trace/tracing_map.c +++ b/kernel/trace/tracing_map.c @@ -454,7 +454,7 @@ static struct tracing_map_elt *get_free_elt(struct trac= ing_map *map) struct tracing_map_elt *elt =3D NULL; int idx; =20 - idx =3D atomic_inc_return(&map->next_elt); + idx =3D atomic_fetch_add_unless(&map->next_elt, 1, map->max_elts); if (idx < map->max_elts) { elt =3D *(TRACING_MAP_ELT(map->elts, idx)); if (map->ops && map->ops->elt_init) @@ -699,7 +699,7 @@ void tracing_map_clear(struct tracing_map *map) { unsigned int i; =20 - atomic_set(&map->next_elt, -1); + atomic_set(&map->next_elt, 0); atomic64_set(&map->hits, 0); atomic64_set(&map->drops, 0); =20 @@ -783,7 +783,7 @@ struct tracing_map *tracing_map_create(unsigned int map= _bits, =20 map->map_bits =3D map_bits; map->max_elts =3D (1 << map_bits); - atomic_set(&map->next_elt, -1); + atomic_set(&map->next_elt, 0); =20 map->map_size =3D (1 << (map_bits + 1)); map->ops =3D ops; --=20 2.18.0