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 459C034B68F; Wed, 3 Dec 2025 16:55:12 +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=1764780912; cv=none; b=OWBNIAxf5R7AToHZrQiqajzy+gVlL77wDsuDLZHHBQJxSbvWWMYA7p8X0YO6u1WUBt9dcb+n3gYpqVbVI9rsxFgf3jOO20waWZ0ITr7xJP/NHm7KaSufg2WZq/CrnbPr2hpvffTD/8mDNjPjDfv2WI5TsvEDusWWSPAQ94jbsp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764780912; c=relaxed/simple; bh=WbLMAwlXP+nhgsgLu5YO9hZgxM0D8b+GU5kXq4X0HxQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Hr7/g+egxbMy6kaa1YMSQ71csPgWh11uMFDXJDgCEEyM1QxgVsJUdPLtK+zDtKNL3uG5j5KjkoD/Ww+8Ws204amX53ZLgnL22pPTOIxP9DYPE2jf8w20agLTUTJEUbikEX1I0gsLjFe3qu9mAjaGynuy4AR3fj1P9f0ayVH/V9A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WMddDpC1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="WMddDpC1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67DCBC4CEF5; Wed, 3 Dec 2025 16:55:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764780911; bh=WbLMAwlXP+nhgsgLu5YO9hZgxM0D8b+GU5kXq4X0HxQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WMddDpC1kmTEWcsP7mrMepoESoqa0tcUzHhYlkOAXhZ94N8HuJ3nVo0QIf9DVlkrd VBHsi1KYG6qU2VDP+UgMAEDf43BbzveYCmuYFcedPtite3fdk0GUPRjgsJRaj10nS4 r5Nd2yuzniEbbsS9e/08neijvhhBRTsQJwSQacZ4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Thomas Zimmermann , Javier Martinez Canillas , Alex Deucher , dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-fbdev@vger.kernel.org, Sasha Levin Subject: [PATCH 6.12 126/132] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Date: Wed, 3 Dec 2025 16:30:05 +0100 Message-ID: <20251203152347.982336576@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251203152343.285859633@linuxfoundation.org> References: <20251203152343.285859633@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Zimmermann [ Upstream commit eb76d0f5553575599561010f24c277cc5b31d003 ] Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB access in fbcon_remap_all(). Without holding the console lock the call races with switching outputs. VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon function uses struct fb_info.node, which is set by register_framebuffer(). As the fb-helper code currently sets up VGA switcheroo before registering the framebuffer, the value of node is -1 and therefore not a legal value. For example, fbcon uses the value within set_con2fb_map() [1] as an index into an array. Moving vga_switcheroo_client_fb_set() after register_framebuffer() can result in VGA switching that does not switch fbcon correctly. Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(), which already holds the console lock. Fbdev calls fbcon_fb_registered() from within register_framebuffer(). Serializes the helper with VGA switcheroo's call to fbcon_remap_all(). Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info as parameter, it really only needs the contained fbcon state. Moving the call to fbcon initialization is therefore cleaner than before. Only amdgpu, i915, nouveau and radeon support vga_switcheroo. For all other drivers, this change does nothing. Signed-off-by: Thomas Zimmermann Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942 # [1] Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)") Acked-by: Javier Martinez Canillas Acked-by: Alex Deucher Cc: dri-devel@lists.freedesktop.org Cc: nouveau@lists.freedesktop.org Cc: amd-gfx@lists.freedesktop.org Cc: linux-fbdev@vger.kernel.org Cc: # v2.6.34+ Link: https://patch.msgid.link/20251105161549.98836-1-tzimmermann@suse.de Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_fb_helper.c | 6 ------ drivers/gpu/drm/i915/display/intel_fbdev.c | 6 ------ drivers/gpu/drm/radeon/radeon_fbdev.c | 5 ----- drivers/video/fbdev/core/fbcon.c | 9 +++++++++ 4 files changed, 9 insertions(+), 17 deletions(-) --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -30,9 +30,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include -#include #include -#include #include #include @@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe strcpy(fb_helper->fb->comm, "[fbcon]"); - /* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */ - if (dev_is_pci(dev->dev)) - vga_switcheroo_client_fb_set(to_pci_dev(dev->dev), fb_helper->info); - return 0; } --- a/drivers/gpu/drm/i915/display/intel_fbdev.c +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c @@ -589,11 +589,8 @@ static int intel_fbdev_restore_mode(stru static void intel_fbdev_client_unregister(struct drm_client_dev *client) { struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); - struct drm_device *dev = fb_helper->dev; - struct pci_dev *pdev = to_pci_dev(dev->dev); if (fb_helper->info) { - vga_switcheroo_client_fb_set(pdev, NULL); drm_fb_helper_unregister_info(fb_helper); } else { drm_fb_helper_unprepare(fb_helper); @@ -620,7 +617,6 @@ static int intel_fbdev_client_hotplug(st { struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); struct drm_device *dev = client->dev; - struct pci_dev *pdev = to_pci_dev(dev->dev); int ret; if (dev->fb_helper) @@ -634,8 +630,6 @@ static int intel_fbdev_client_hotplug(st if (ret) goto err_drm_fb_helper_fini; - vga_switcheroo_client_fb_set(pdev, fb_helper->info); - return 0; err_drm_fb_helper_fini: --- a/drivers/gpu/drm/radeon/radeon_fbdev.c +++ b/drivers/gpu/drm/radeon/radeon_fbdev.c @@ -300,10 +300,8 @@ static void radeon_fbdev_client_unregist { struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); struct drm_device *dev = fb_helper->dev; - struct radeon_device *rdev = dev->dev_private; if (fb_helper->info) { - vga_switcheroo_client_fb_set(rdev->pdev, NULL); drm_helper_force_disable_all(dev); drm_fb_helper_unregister_info(fb_helper); } else { @@ -325,7 +323,6 @@ static int radeon_fbdev_client_hotplug(s { struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); struct drm_device *dev = client->dev; - struct radeon_device *rdev = dev->dev_private; int ret; if (dev->fb_helper) @@ -342,8 +339,6 @@ static int radeon_fbdev_client_hotplug(s if (ret) goto err_drm_fb_helper_fini; - vga_switcheroo_client_fb_set(rdev->pdev, fb_helper->info); - return 0; err_drm_fb_helper_fini: --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -65,6 +65,7 @@ #include #include #include +#include #include #include #include @@ -77,6 +78,7 @@ #include #include /* For counting font checksums */ #include +#include #include #include "fbcon.h" @@ -2894,6 +2896,9 @@ void fbcon_fb_unregistered(struct fb_inf console_lock(); + if (info->device && dev_is_pci(info->device)) + vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL); + fbcon_registered_fb[info->node] = NULL; fbcon_num_registered_fb--; @@ -3027,6 +3032,10 @@ static int do_fb_registered(struct fb_in } } + /* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */ + if (info->device && dev_is_pci(info->device)) + vga_switcheroo_client_fb_set(to_pci_dev(info->device), info); + return ret; }