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 389991E7C03; Mon, 1 Dec 2025 22:51:27 +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=1764629488; cv=none; b=Y2n1oOd6Ea+w1EtsUBA2Bo0ZIoyv8GdPUECTyZKVZWXBiq5Dv0mrAZr1ACXdvK9isUs+ERXCSTHr694uW8OCqGtaWhfSzJs9+9F1QV+wdfRsaveSAshUbI2GlYB0s2r7q/g6wR85Gz4EnH3eL+9urjcP1vrcM8wingaBZ8YIoQ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764629488; c=relaxed/simple; bh=l6a8KE0SQRDdJHNwVx3ilxUBBg9ZsFk4iQ3P3jn1cCY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Fsoo1VmJI6nyL7x55kQiw3AxO8LDON5cANgY4ysQjq0Apq6hBcDk1Tg0nH0k+3i6qHfAClkj4VT6rmHMllazR3VNGjlAU2l9UtWbhDpESrWGYi2OefqDknuAib2oirPD2yLs5l5tZcLEuzk5tx/pnPdcWOlQmCvZq3yDEtWxRew= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m5udlNqh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m5udlNqh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A4C2C4CEF1; Mon, 1 Dec 2025 22:51:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764629487; bh=l6a8KE0SQRDdJHNwVx3ilxUBBg9ZsFk4iQ3P3jn1cCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=m5udlNqhOrxeKfPmSLeccLSvSbqX5+SiNB77oiTf24gMs1cf1t5NcVT6y2WEvzJcn v92rwC/DkEMb8tvON1+nh7wcDrKL7m3oHwEcjBGzj+grL/h1naoAMaQO67shLT2eX1 x8sM289OhNRbzRN2I+nMyMIftlJDjPTtg8S2w7prKksUVPPnIk2GSFdhqD2ZRZZOaO sSHzdN8o0sWV+eahBnjF4R6tEoRwsKXa8mJ8G/9h5qLUTXj9eS/VpzYl6rm9ip9zxY sC6Mvqj9PboKAgZuFbe08GzjLV43HbaeYnZOJcGoSHeazH6BHYJMpqmhGJvf3U3O+n wtgMtOsy7fDnA== From: Sasha Levin To: stable@vger.kernel.org Cc: 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 6.6.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Date: Mon, 1 Dec 2025 17:51:23 -0500 Message-ID: <20251201225123.1298682-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025120119-quake-universal-d896@gregkh> References: <2025120119-quake-universal-d896@gregkh> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 [ drm_fb_helper_unregister_info() lacks vga_switcheroo code ] Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_fb_helper.c | 7 ------- drivers/video/fbdev/core/fbcon.c | 9 +++++++++ 2 files changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index b507c1c008a3e..3891837a78414 100644 --- 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 @@ -1668,7 +1666,6 @@ static int drm_fb_helper_find_sizes(struct drm_fb_helper *fb_helper, 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; int ret; @@ -1687,10 +1684,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper) 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; } diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 78a5b22c8d150..8b2c3065c0c26 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include #include @@ -75,6 +76,7 @@ #include #include /* For counting font checksums */ #include +#include #include #include "fbcon.h" @@ -2913,6 +2915,9 @@ 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--; @@ -3046,6 +3051,10 @@ 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; } -- 2.51.0