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 2C97ED11700 for ; Tue, 2 Dec 2025 08:16:25 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 65A6B10E5A4; Tue, 2 Dec 2025 08:16:24 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="CLhzbIrD"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id C812410E429; Mon, 1 Dec 2025 16:11:45 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id EC1186016B; Mon, 1 Dec 2025 16:11:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7491C4CEF1; Mon, 1 Dec 2025 16:11:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764605504; bh=hP6L2O0FOWlifqFD5YvpPXkCFTX0ufmIW1euI1UobFE=; h=Subject:To:Cc:From:Date:From; b=CLhzbIrDgV/5rXVseNlhnHM3u6z8oGrim+xh2g7+i9uAsTmVloDxALHxNYw0ahbxn MdTupXhUXdKKGoI/gmJnmm3yd1dpAYERzTINECCkr5+mOMfjpu7Mn7ym/Z95QsXf+3 FhQ1V5OvgJ7UiLEgzdBvNVXb26eDM/kT5j4BeK3g= Subject: Patch "drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup" has been added to the 6.17-stable tree To: alexander.deucher@amd.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, gregkh@linuxfoundation.org, javierm@redhat.com, nouveau@lists.freedesktop.org, tzimmermann@suse.de Cc: From: Date: Mon, 01 Dec 2025 17:08:12 +0100 Message-ID: <2025120112-squealing-profound-4cd0@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore X-Mailman-Approved-At: Tue, 02 Dec 2025 08:16:18 +0000 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" This is a note to let you know that I've just added the patch titled drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup to the 6.17-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-fbcon-vga_switcheroo-avoid-race-condition-in-fbcon-setup.patch and it can be found in the queue-6.17 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From eb76d0f5553575599561010f24c277cc5b31d003 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 5 Nov 2025 17:14:49 +0100 Subject: drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup From: Thomas Zimmermann commit eb76d0f5553575599561010f24c277cc5b31d003 upstream. 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: Greg Kroah-Hartman --- drivers/gpu/drm/drm_fb_helper.c | 14 -------------- drivers/video/fbdev/core/fbcon.c | 9 +++++++++ 2 files changed, 9 insertions(+), 14 deletions(-) --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -31,9 +31,7 @@ #include #include -#include #include -#include #include #include @@ -566,11 +564,6 @@ EXPORT_SYMBOL(drm_fb_helper_release_info */ void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper) { - struct fb_info *info = fb_helper->info; - struct device *dev = info->device; - - if (dev_is_pci(dev)) - vga_switcheroo_client_fb_set(to_pci_dev(dev), NULL); unregister_framebuffer(fb_helper->info); } EXPORT_SYMBOL(drm_fb_helper_unregister_info); @@ -1632,7 +1625,6 @@ static int drm_fb_helper_single_fb_probe struct drm_client_dev *client = &fb_helper->client; struct drm_device *dev = fb_helper->dev; struct drm_fb_helper_surface_size sizes; - struct fb_info *info; int ret; if (drm_WARN_ON(dev, !dev->driver->fbdev_probe)) @@ -1653,12 +1645,6 @@ static int drm_fb_helper_single_fb_probe strcpy(fb_helper->fb->comm, "[fbcon]"); - info = fb_helper->info; - - /* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */ - if (dev_is_pci(info->device)) - vga_switcheroo_client_fb_set(to_pci_dev(info->device), info); - return 0; } --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -66,6 +66,7 @@ #include #include #include +#include #include #include #include @@ -78,6 +79,7 @@ #include #include /* For counting font checksums */ #include +#include #include #include "fbcon.h" @@ -2906,6 +2908,9 @@ 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--; @@ -3039,6 +3044,10 @@ 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; } Patches currently in stable-queue which might be from tzimmermann@suse.de are queue-6.17/drm-fbcon-vga_switcheroo-avoid-race-condition-in-fbcon-setup.patch