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 8B16ED116F1 for ; Mon, 1 Dec 2025 22:11:03 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A8C7010E4AA; Mon, 1 Dec 2025 22:11:01 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="BxSfazRK"; 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 7E0D410E4BF; Mon, 1 Dec 2025 22:11:00 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 879F960157; Mon, 1 Dec 2025 22:10:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C18AAC116D0; Mon, 1 Dec 2025 22:10:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764627059; bh=j2D3hRBZI5QkXGbuJwMdox5sp0EOC/YYi/24i9XPVls=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BxSfazRKrSH4APxJ/dXczuqSQ9UktoWUdTk0Lz9eX1/08bq8zgt1nFr7l1MRQkFwz ZsICotIcfK2eXu8rHkeTInPj5aU48rwnfHg1Q3Cd7hGkT0qz6B0n7prNtC7sHo2air JdinlaARGiKsKFL47f3e3Alv5ruociYZWmzhbRP10Q5KUT7hW1pZto3ADDPWjWu9YH X5co8WT0XHExU0qgNlZx6142gElc18YKfulT2oS+KvQT81v9vlDdfYEi/ycDoKmEGq f+aBlauMSk7922HkRWLbu6YXsW8RSnn3t4h7sqIse33e1Emi7GlF+nuQbivkJBNkvI oDbqsBH73NZTA== 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 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Date: Mon, 1 Dec 2025 17:10:55 -0500 Message-ID: <20251201221055.1281985-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025120119-edgy-recycled-bcfe@gregkh> References: <2025120119-edgy-recycled-bcfe@gregkh> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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" 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 [ adapted dev->dev variable access ] Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_fb_helper.c | 6 ------ drivers/video/fbdev/core/fbcon.c | 9 +++++++++ 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index b15ddbd65e7b5..a8971c4eb9f05 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 @@ -1637,10 +1635,6 @@ 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 1fc1e47ae2b49..e681066736dea 100644 --- 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_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--; @@ -3027,6 +3032,10 @@ 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