From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 028B7CF3186 for ; Wed, 19 Nov 2025 09:47:03 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 900E610E038; Wed, 19 Nov 2025 09:47:03 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="GDW5Ka2y"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) by gabe.freedesktop.org (Postfix) with ESMTPS id A4BEB10E038; Wed, 19 Nov 2025 09:47:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1763545622; x=1795081622; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=D7gnoA6XN1BAzrK8g+v2VbFkaVSefz2D5SB00zEFA1o=; b=GDW5Ka2yIfvomF96pEz6WKoupdw/+LHEI7iZSbrHQWJyVLZ5vLdrJb/m oYf7Cb1c+KrMnpKmKdBYqMDdCtebzprfOERBcUC1MLIGPA43/5zrsyB+I hSofR8nvtN+D62UwNINebQqo9cPKqRroq5HhhhHy6U00iowiCPRaupH2m B+vUrnphMAwM9S1tKjPICDCeE0nEG4+3zj0f5Hm9Tk4WKGCTXg8sq24re dXu6t7fZGj3qyW8N9aDblc9XbYddXqbRgCj7dt8jVdysB9Vz1Mn/zPVEU DBGLypTOojHANz/8nXyAtSYGTBriSZrx3ruxzr0qGuIocGe21Q56ziW/D g==; X-CSE-ConnectionGUID: FNtlYi7fT4Cghikk3V57WA== X-CSE-MsgGUID: RE3TbRFsTRah6gcBsE/S/g== X-IronPort-AV: E=McAfee;i="6800,10657,11617"; a="77039209" X-IronPort-AV: E=Sophos;i="6.19,315,1754982000"; d="scan'208";a="77039209" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Nov 2025 01:47:01 -0800 X-CSE-ConnectionGUID: KmyDeXwSRmm+onoQJ5DniA== X-CSE-MsgGUID: aTM+7yp9T9qd9AahYnOH2A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,315,1754982000"; d="scan'208";a="221918175" Received: from kandpal-x299-ud4-pro.iind.intel.com ([10.190.239.10]) by fmviesa001.fm.intel.com with ESMTP; 19 Nov 2025 01:46:59 -0800 From: Suraj Kandpal To: dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Cc: ankit.k.nautiyal@intel.com, arun.r.murthy@intel.com, imre.deak@intel.com, Suraj Kandpal Subject: [PATCH v2] drm/display/dp_mst: Add protection against 0 vcpi Date: Wed, 19 Nov 2025 15:16:50 +0530 Message-Id: <20251119094650.799135-1-suraj.kandpal@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251113043918.716367-1-suraj.kandpal@intel.com> References: <20251113043918.716367-1-suraj.kandpal@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" When releasing a timeslot there is a slight chance we may end up with the wrong payload mask due to overflow if the delayed_destroy_work ends up coming into play after a DP 2.1 monitor gets disconnected which causes vcpi to become 0 then we try to make the payload = ~BIT(vcpi - 1) which is a negative shift. VCPI id should never really be 0 hence skip changing the payload mask if VCPI is 0. Otherwise it leads to <7> [515.287237] xe 0000:03:00.0: [drm:drm_dp_mst_get_port_malloc [drm_display_helper]] port ffff888126ce9000 (3) <4> [515.287267] -----------[ cut here ]----------- <3> [515.287268] UBSAN: shift-out-of-bounds in ../drivers/gpu/drm/display/drm_dp_mst_topology.c:4575:36 <3> [515.287271] shift exponent -1 is negative <4> [515.287275] CPU: 7 UID: 0 PID: 3108 Comm: kworker/u64:33 Tainted: G S U 6.17.0-rc6-lgci-xe-xe-3795-3e79699fa1b216e92+ #1 PREEMPT(voluntary) <4> [515.287279] Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER <4> [515.287279] Hardware name: ASUS System Product Name/PRIME Z790-P WIFI, BIOS 1645 03/15/2024 <4> [515.287281] Workqueue: drm_dp_mst_wq drm_dp_delayed_destroy_work [drm_display_helper] <4> [515.287303] Call Trace: <4> [515.287304] <4> [515.287306] dump_stack_lvl+0xc1/0xf0 <4> [515.287313] dump_stack+0x10/0x20 <4> [515.287316] __ubsan_handle_shift_out_of_bounds+0x133/0x2e0 <4> [515.287324] ? drm_atomic_get_private_obj_state+0x186/0x1d0 <4> [515.287333] drm_dp_atomic_release_time_slots.cold+0x17/0x3d [drm_display_helper] <4> [515.287355] mst_connector_atomic_check+0x159/0x180 [xe] <4> [515.287546] drm_atomic_helper_check_modeset+0x4d9/0xfa0 <4> [515.287550] ? __ww_mutex_lock.constprop.0+0x6f/0x1a60 <4> [515.287562] intel_atomic_check+0x119/0x2b80 [xe] <4> [515.287740] ? find_held_lock+0x31/0x90 <4> [515.287747] ? lock_release+0xce/0x2a0 <4> [515.287754] drm_atomic_check_only+0x6a2/0xb40 <4> [515.287758] ? drm_atomic_add_affected_connectors+0x12b/0x140 <4> [515.287765] drm_atomic_commit+0x6e/0xf0 <4> [515.287766] ? _pfx__drm_printfn_info+0x10/0x10 <4> [515.287774] drm_client_modeset_commit_atomic+0x25c/0x2b0 <4> [515.287794] drm_client_modeset_commit_locked+0x60/0x1b0 <4> [515.287795] ? mutex_lock_nested+0x1b/0x30 <4> [515.287801] drm_client_modeset_commit+0x26/0x50 <4> [515.287804] __drm_fb_helper_restore_fbdev_mode_unlocked+0xdc/0x110 <4> [515.287810] drm_fb_helper_hotplug_event+0x120/0x140 <4> [515.287814] drm_fbdev_client_hotplug+0x28/0xd0 <4> [515.287819] drm_client_hotplug+0x6c/0xf0 <4> [515.287824] drm_client_dev_hotplug+0x9e/0xd0 <4> [515.287829] drm_kms_helper_hotplug_event+0x1a/0x30 <4> [515.287834] drm_dp_delayed_destroy_work+0x3df/0x410 [drm_display_helper] <4> [515.287861] process_one_work+0x22b/0x6f0 <4> [515.287874] worker_thread+0x1e8/0x3d0 <4> [515.287879] ? __pfx_worker_thread+0x10/0x10 <4> [515.287882] kthread+0x11c/0x250 <4> [515.287886] ? __pfx_kthread+0x10/0x10 <4> [515.287890] ret_from_fork+0x2d7/0x310 <4> [515.287894] ? __pfx_kthread+0x10/0x10 <4> [515.287897] ret_from_fork_asm+0x1a/0x30 Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6303 Signed-off-by: Suraj Kandpal --- v1 -> v2: -Add the call trace and closes tag [Jani] -Change payload mask only is vcpi > 0 [Imre] drivers/gpu/drm/display/drm_dp_mst_topology.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c index 64e5c176d5cc..be749dcad3b5 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -4572,7 +4572,8 @@ int drm_dp_atomic_release_time_slots(struct drm_atomic_state *state, if (!payload->delete) { payload->pbn = 0; payload->delete = true; - topology_state->payload_mask &= ~BIT(payload->vcpi - 1); + if (payload->vcpi > 0) + topology_state->payload_mask &= ~BIT(payload->vcpi - 1); } return 0; -- 2.34.1