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 C915478F5D for ; Mon, 1 Dec 2025 16:01:34 +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=1764604894; cv=none; b=dkrH6oYwstduAbPPtOhi890u3vXRCxjwg9UoU6XBKsbHOm4JtXsGW/mNqxmwYWPQEknRegqbT5UpSoG2kCKTzoW4jBP7rc7IT3tg6/QvSaH11zYgMsgP5KAGxHAFZi1A21Jd9SAi8QZYHcvsiFYpCoUwOCaGSZA8PTyzimnwO0o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764604894; c=relaxed/simple; bh=Szk9gkOM4FXwYsOaY1M4KM0DDuEGa2CgKkRwLwJeEoc=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=AzY+NHOBFMaMmwM9s+P8lBKetvsdMASWVmz6J/IMuk73rwMM/v2MaZOcC/JJd6P8uZH7DWiCpAHjU7HSi9MvOHoNTX4gZKIufoHLa0Q0cP70EBbfW9nZrdpHU+yoYB06pfPZ5IC/y5E4nVjeEjqnvvoh+0e/ei35lrP6eYgKGw0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=A8h/W/c+; 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="A8h/W/c+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD0EEC4CEF1; Mon, 1 Dec 2025 16:01:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764604894; bh=Szk9gkOM4FXwYsOaY1M4KM0DDuEGa2CgKkRwLwJeEoc=; h=Subject:To:Cc:From:Date:From; b=A8h/W/c+85lgyg+LJn24hwJzcZeB6nGgp1ecl3XvEuDsKuc/Q0WUl3Vivwm/L2Nwm JwG7fzmvVNxbxSkMjh/bCNOqeZR75ozu2YQLTUDoso4+6savGgBNZvioyAO/H0twpP 7MlNnVodY8qnrCyM6IUvPPjkamULb9PuMVoouW1Y= Subject: FAILED: patch "[PATCH] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon" failed to apply to 6.1-stable tree To: tzimmermann@suse.de,alexander.deucher@amd.com,javierm@redhat.com,stable@vger.kernel.org Cc: From: Date: Mon, 01 Dec 2025 17:01:20 +0100 Message-ID: <2025120120-clunky-padded-4436@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x eb76d0f5553575599561010f24c277cc5b31d003 # git commit -s git send-email --to '' --in-reply-to '2025120120-clunky-padded-4436@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From eb76d0f5553575599561010f24c277cc5b31d003 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 5 Nov 2025 17:14:49 +0100 Subject: [PATCH] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup 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 diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 11a5b60cb9ce..0b3ee008523d 100644 --- 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_fb_helper *fb_helper) 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(struct drm_fb_helper *fb_helper) 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; } diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 9bd3c3814b5c..e7e07eb2142e 100644 --- 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" @@ -2899,6 +2901,9 @@ void fbcon_fb_unregistered(struct fb_info *info) 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--; @@ -3032,6 +3037,10 @@ static int do_fb_registered(struct fb_info *info) } } + /* 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; }