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 2F34033033B; Wed, 3 Dec 2025 15:52:08 +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=1764777128; cv=none; b=kxtlL4Cl8kfG+MnNz5z/VygafykseJhs5wP5hf5d2GM0ttH8obBiMPHNvSePhEH+ijDS1Qsm+XEq94pdjp9SfAyCNeOcCZgFnkd4vxpF7WO2UO/Kl8TurBpKK1Jb4FmfSqSOp4P8hFNFZfW+f0iEkaPRMnax8LM3+i45o05JI8M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764777128; c=relaxed/simple; bh=YChEWkKxygULu9HXbwc6YSvoGwoyOh7/HA7GfIA3z60=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XkOS3F2xco5RZe5aK9noWCr+zPIRrhS9h2gZlL6qyBlif2TOUuzjbBo83GthjeZHbZmAzFBRUeeQMqwyvVr3i8EGYlE/mpae88WNfv0QPFHHGpahqZaCNqz8TGatR/x7ZLYki1I73Hf4e0jigKVv9dIibWb7jksZnXjd+WwMiTk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ih4A6LCo; 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="ih4A6LCo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F894C4CEF5; Wed, 3 Dec 2025 15:52:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764777128; bh=YChEWkKxygULu9HXbwc6YSvoGwoyOh7/HA7GfIA3z60=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ih4A6LCor/zR3bo6gzm2i2uiMj1hEHR2GelGbhIHRC1ksnYtbwLVdiGk0LklEvfL2 LVNTxKhwcswWDhu1J2FMo3I3ZOp9ZJzgmEY61vTU6lbBO8OaWzjWrj8aX5EBGqRwcz 8yCLdtBD3gTpZyOYdRlKCNHW2eFEYjh4jic/wPUY= 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 Subject: [PATCH 6.17 090/146] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Date: Wed, 3 Dec 2025 16:27:48 +0100 Message-ID: <20251203152349.753412961@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251203152346.456176474@linuxfoundation.org> References: <20251203152346.456176474@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ 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; }