From patchwork Wed Oct 9 05:23:31 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fei Shao X-Patchwork-Id: 13827546 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 A88A1CF0444 for ; Wed, 9 Oct 2024 05:24:43 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1248510E205; Wed, 9 Oct 2024 05:24:43 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.b="S8IupSCb"; dkim-atps=neutral Received: from mail-pg1-f178.google.com (mail-pg1-f178.google.com [209.85.215.178]) by gabe.freedesktop.org (Postfix) with ESMTPS id 590AF10E646 for ; Wed, 9 Oct 2024 05:24:41 +0000 (UTC) Received: by mail-pg1-f178.google.com with SMTP id 41be03b00d2f7-7e9e38dd5f1so4790874a12.0 for ; Tue, 08 Oct 2024 22:24:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1728451481; x=1729056281; darn=lists.freedesktop.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=7A6H+KzAjmDQU5CdelmQUCc3Y+xjatMunsXRFdXtofI=; b=S8IupSCbtDq6Ep8IGCKrs8KQjQmkRuwkF7/De6BwkVzmF+j1iIEY9yxaffOYz84O+o Fyiz9XvXjS6z2l6FvG29FI2oqrzzPO33LE0mNWl0oLEcN49z3LIUcunNPDqk6UnLHEJo LgzKDrUDvHBF/UvgXDw1nLzQ9aXsoCWK35veE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728451481; x=1729056281; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=7A6H+KzAjmDQU5CdelmQUCc3Y+xjatMunsXRFdXtofI=; b=AqJbFcQtf3UgFfc3o8deCgbRWwwzLj4sf8J5l4QLw1QixIRXiVVj9mTerwav3Gr8ES ogXZe3TLdePKKbDmGz8yzLn9xNVV8upwlCaeE5H3gJskeR1PLykGo4e8zo3nj0OUlXCl VIrZnGQSEBYbhVs+V2bxXQyEPduS9HSogVUGqk/l32tV+vnMRuonrgX/+dpNPKjn6inR NnWrWSMyWmcX62ALTtoyauPCHgKsqeu9yddijTCWgHCyAcnv27Rz9fjpMHTpuEdbBpLV CFOWHd3/HYdm8JRxb/GhRnxBq1IwbMcBZxD7Y42ni/D1LbAQXkkovzhHL4ydGz3gy3Ej r4Xg== X-Forwarded-Encrypted: i=1; AJvYcCWMIxEpFkKVWH79zdYIV0wzD4G7xxVtWyNvbBfzcDudeFQUGh6+wJxViyzB8YoUXx++InVZ+IM8s3w=@lists.freedesktop.org X-Gm-Message-State: AOJu0YxWQksnUj1jq8/6mvStpmTgmZ2cBxtGN+N9h+xXZEmKyiKjR2Ml AUIoBP3rKs6ZyqSWCqqZV2BKYuPyrv5BxZ8Xh/eshA43D29PIKY092wu5xkqBA5jCW2G62VtMGP 1YA== X-Google-Smtp-Source: AGHT+IEKD21DoJeYdl5yUlTRJTAGnxFTDW05PgaoJ5dAAeoH/tToyjk8YeS0tkwuwuWsScTJVYPC5Q== X-Received: by 2002:a05:6a21:3944:b0:1cf:3d14:6921 with SMTP id adf61e73a8af0-1d8a3c5a65bmr2666769637.35.1728451480803; Tue, 08 Oct 2024 22:24:40 -0700 (PDT) Received: from fshao-p620.tpe.corp.google.com ([2401:fa00:1:10:3386:622d:881d:c6f1]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71e008f3705sm5077341b3a.109.2024.10.08.22.24.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Oct 2024 22:24:40 -0700 (PDT) From: Fei Shao To: Andrzej Hajda , Neil Armstrong , Robert Foss , Maxime Ripard , Laurent Pinchart Cc: Chen-Yu Tsai , AngeloGioacchino Del Regno , Fei Shao , David Airlie , Jernej Skrabec , Jonas Karlman , Maarten Lankhorst , Simona Vetter , Thomas Zimmermann , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH] drm/bridge: panel: Use devm_drm_bridge_add() Date: Wed, 9 Oct 2024 13:23:31 +0800 Message-ID: <20241009052402.411978-1-fshao@chromium.org> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" In the mtk_dsi driver, its DSI host attach callback calls devm_drm_of_get_bridge() to get the next bridge. If that next bridge is a panel bridge, a panel_bridge object is allocated and managed by the panel device. Later, if the attach callback fails with -EPROBE_DEFER from subsequent component_add(), the panel device invoking the callback at probe time also fails, and all device-managed resources are freed accordingly. This exposes a drm_bridge bridge_list corruption due to the unbalanced lifecycle between the DSI host and the panel devices: the panel_bridge object managed by panel device is freed, while drm_bridge_remove() is bound to DSI host device and never gets called. The next drm_bridge_add() will trigger UAF against the freed bridge list object and result in kernel panic. This bug is observed on a MediaTek MT8188-based Chromebook with MIPI DSI outputting to a DSI panel (DT is WIP for upstream). As a fix, using devm_drm_bridge_add() with the panel device in the panel path seems reasonable. This also implies a chain of potential cleanup actions: 1. Removing drm_bridge_remove() means devm_drm_panel_bridge_release() becomes hollow and can be removed. 2. devm_drm_panel_bridge_add_typed() is almost emptied except for the `bridge->pre_enable_prev_first` line. Itself can be also removed if we move the line into drm_panel_bridge_add_typed(). (maybe?) 3. drm_panel_bridge_add_typed() now calls all the needed devm_* calls, so it's essentially the new devm_drm_panel_bridge_add_typed(). 4. drmm_panel_bridge_add() needs to be updated accordingly since it calls drm_panel_bridge_add_typed(). But now there's only one bridge object to be freed, and it's already being managed by panel device. I wonder if we still need both drmm_ and devm_ version in this case. (maybe yes from DRM PoV, I don't know much about the context) This is a RFC patch since I'm not sure if my understanding is correct (for both the fix and the cleanup). It fixes the issue I encountered, but I don't expect it to be picked up directly due to the redundant commit message and the dangling devm_drm_panel_bridge_release(). I plan to resend the official patch(es) once I know what I supposed to do next. For reference, here's the KASAN report from the device: ================================================================== BUG: KASAN: slab-use-after-free in drm_bridge_add+0x98/0x230 Read of size 8 at addr ffffff80c4e9e100 by task kworker/u32:1/69 CPU: 1 UID: 0 PID: 69 Comm: kworker/u32:1 Not tainted 6.12.0-rc1-next-20241004-kasan-00030-g062135fa4046 #1 Hardware name: Google Ciri sku0/unprovisioned board (DT) Workqueue: events_unbound deferred_probe_work_func Call trace: dump_backtrace+0xfc/0x140 show_stack+0x24/0x38 dump_stack_lvl+0x40/0xc8 print_report+0x140/0x700 kasan_report+0xcc/0x130 __asan_report_load8_noabort+0x20/0x30 drm_bridge_add+0x98/0x230 devm_drm_panel_bridge_add_typed+0x174/0x298 devm_drm_of_get_bridge+0xe8/0x190 mtk_dsi_host_attach+0x130/0x2b0 mipi_dsi_attach+0x8c/0xe8 hx83102_probe+0x1a8/0x368 mipi_dsi_drv_probe+0x6c/0x88 really_probe+0x1c4/0x698 __driver_probe_device+0x160/0x298 driver_probe_device+0x7c/0x2a8 __device_attach_driver+0x2a0/0x398 bus_for_each_drv+0x198/0x200 __device_attach+0x1c0/0x308 device_initial_probe+0x20/0x38 bus_probe_device+0x11c/0x1f8 deferred_probe_work_func+0x80/0x250 worker_thread+0x9b4/0x2780 kthread+0x274/0x350 ret_from_fork+0x10/0x20 Allocated by task 69: kasan_save_track+0x40/0x78 kasan_save_alloc_info+0x44/0x58 __kasan_kmalloc+0x84/0xa0 __kmalloc_node_track_caller_noprof+0x228/0x450 devm_kmalloc+0x6c/0x288 devm_drm_panel_bridge_add_typed+0xa0/0x298 devm_drm_of_get_bridge+0xe8/0x190 mtk_dsi_host_attach+0x130/0x2b0 mipi_dsi_attach+0x8c/0xe8 hx83102_probe+0x1a8/0x368 mipi_dsi_drv_probe+0x6c/0x88 really_probe+0x1c4/0x698 __driver_probe_device+0x160/0x298 driver_probe_device+0x7c/0x2a8 __device_attach_driver+0x2a0/0x398 bus_for_each_drv+0x198/0x200 __device_attach+0x1c0/0x308 device_initial_probe+0x20/0x38 bus_probe_device+0x11c/0x1f8 deferred_probe_work_func+0x80/0x250 worker_thread+0x9b4/0x2780 kthread+0x274/0x350 ret_from_fork+0x10/0x20 Freed by task 69: kasan_save_track+0x40/0x78 kasan_save_free_info+0x58/0x78 __kasan_slab_free+0x48/0x68 kfree+0xd4/0x750 devres_release_all+0x144/0x1e8 really_probe+0x48c/0x698 __driver_probe_device+0x160/0x298 driver_probe_device+0x7c/0x2a8 __device_attach_driver+0x2a0/0x398 bus_for_each_drv+0x198/0x200 __device_attach+0x1c0/0x308 device_initial_probe+0x20/0x38 bus_probe_device+0x11c/0x1f8 deferred_probe_work_func+0x80/0x250 worker_thread+0x9b4/0x2780 kthread+0x274/0x350 ret_from_fork+0x10/0x20 The buggy address belongs to the object at ffffff80c4e9e000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 256 bytes inside of freed 4096-byte region [ffffff80c4e9e000, ffffff80c4e9f000) The buggy address belongs to the physical page: head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x8000000000000040(head|zone=2) page_type: f5(slab) page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x104e98 raw: 8000000000000040 ffffff80c0003040 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000 head: 8000000000000040 ffffff80c0003040 dead000000000122 0000000000000000 head: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000 head: 8000000000000003 fffffffec313a601 ffffffffffffffff 0000000000000000 head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffffff80c4e9e000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffffff80c4e9e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffffff80c4e9e100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffffff80c4e9e180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffffff80c4e9e200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb =================================================================== Signed-off-by: Fei Shao --- drivers/gpu/drm/bridge/panel.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c index 6e88339dec0f..352723c59c70 100644 --- a/drivers/gpu/drm/bridge/panel.c +++ b/drivers/gpu/drm/bridge/panel.c @@ -303,7 +303,7 @@ struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel, panel_bridge->bridge.ops = DRM_BRIDGE_OP_MODES; panel_bridge->bridge.type = connector_type; - drm_bridge_add(&panel_bridge->bridge); + devm_drm_bridge_add(panel->dev, &panel_bridge->bridge); return &panel_bridge->bridge; } @@ -327,7 +327,6 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge) panel_bridge = drm_bridge_to_panel_bridge(bridge); - drm_bridge_remove(bridge); devm_kfree(panel_bridge->panel->dev, bridge); } EXPORT_SYMBOL(drm_panel_bridge_remove); @@ -359,8 +358,6 @@ static void devm_drm_panel_bridge_release(struct device *dev, void *res) if (!bridge) return; - - drm_bridge_remove(bridge); } /**