From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9FB18326D63 for ; Sat, 28 Feb 2026 17:49:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300979; cv=none; b=dYVS/nZH5ARfuzO7mThEg0Yo/uglsmj4bQ252IozZwUZ2I8bxeXp/q5CnrlDaj90ykepsgZlgH7Ed/HkTfxYzKtsaolvxw1C5S0X5p03wIYKksj7Al8vg4T4P+Mx6YtWUE/XnMFEii6Rc8D0VURM6hRyNjolzM2y5NDn3fJEp8U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300979; c=relaxed/simple; bh=FY8CeVY88weBCGa2RQnVCBng5D48wMZTOLCW68rPoiI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uh0j5ShUsmSMtACbdnppcA47h3oj/BFLQnwIQ4Sb5HhXa8+GPa2cBShMdzudLXhBVNXpqoN8heGzSUMINbpOlXhLGYFtxJbEm2az8t+FqsQmn6t80CcI3uermW6Y+1Fa84O/yqyHuSPUD+Hv3fGxfib+x4iZ5HtfsBfoqoA/snY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IdEDdEFV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IdEDdEFV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECC18C2BC87; Sat, 28 Feb 2026 17:49:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300979; bh=FY8CeVY88weBCGa2RQnVCBng5D48wMZTOLCW68rPoiI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IdEDdEFVSeXSEmmc7l3aqTD2CQg4KyLPsd6r06wqYgT66i0Xs5O70BhE221pTw0uh nwp4IlWbT+7FckoZjtuLgnmnYMkL1iX7y2paN8XRdasy3NKvu3EYUIJutqUuLZMlZ6 2lXjIHuAg8tEGBPObe+GxH4XR4/4Cy+hmXuCscZSd4EEdC9+23XIeaLJ6wBiTIidYF a9yLnitzJHP+gC2nRkYS+oezu2f5QYqy/LK44O71Ai8jiSIZizKM6rihD1ydvAbuMx goWhMYmR6iTOOGv1aZjPrAZeB+31zlRHSKLZ1GvLplsxMp+M5BEqsCVm8svnwMb+H0 D6EgWw6jSWZWA== From: Sasha Levin To: patches@lists.linux.dev Cc: Suraj Kandpal , Imre Deak , Lyude Paul , Sasha Levin Subject: [PATCH 6.18 108/752] drm/display/dp_mst: Add protection against 0 vcpi Date: Sat, 28 Feb 2026 12:36:59 -0500 Message-ID: <20260228174750.1542406-108-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228174750.1542406-1-sashal@kernel.org> References: <20260228174750.1542406-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Suraj Kandpal [ Upstream commit 342ccffd9f77fc29fe1c05fd145e4d842bd2feaa ] 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 Reviewed-by: Imre Deak Reviewed-by: Lyude Paul Link: https://patch.msgid.link/20251119094650.799135-1-suraj.kandpal@intel.com Signed-off-by: Sasha Levin --- 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 64e5c176d5cce..be749dcad3b58 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; -- 2.51.0