From patchwork Mon Jan 31 21:05:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12731162 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46C48C433EF for ; Mon, 31 Jan 2022 21:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381110AbiAaVHf (ORCPT ); Mon, 31 Jan 2022 16:07:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379972AbiAaVGv (ORCPT ); Mon, 31 Jan 2022 16:06:51 -0500 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E0A7C06176D for ; Mon, 31 Jan 2022 13:06:49 -0800 (PST) Received: by mail-wm1-x333.google.com with SMTP id o1-20020a1c4d01000000b0034d95625e1fso284129wmh.4 for ; Mon, 31 Jan 2022 13:06:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=3hWiJw8I0v/FhKndgqc2O30e2FmZYwhYniGtWb90tWY=; b=HHQSy572JqEYwMH+XAImxbYANsnDK/FocLe1VGb5+1HoyTQOlf6pkJdzMLp+bQVtjl 6nGB7Yu3HDEDy7AAoG4b1oLVSDRpa9s5ddsKnU8r6m1P82LiOt+SAZcWqZYeQWPQARgU WXr3wNTQE3KehfvQbrgyI6k9xn3+ZGRP2IBiM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=3hWiJw8I0v/FhKndgqc2O30e2FmZYwhYniGtWb90tWY=; b=ypZ4FCGKet2NYP6sH3ww6IMIZS8NCL8oY/1hCspr4+7c+aXSn9aCwOFpryhUwHVseh wkOMvdmn/gRxpukOfAJyjAe96Kfxy4r2lvqDDsfbpUwYXVQBeuUU078QhUDFf4OTPr7Y gZre1scAsiSNBpUA0GO1ihY2J5En0myzhhfZxy+82QEDkaLpXYhcK4Hxvtrv/pN7m85c QqiisjQfxSBGIme+QzF8AXW0d/AB+NtBVFjv23IbViZg7dy8C43HmmR3Cns2wpZpqG4A HjuFvSXjwznXYKILeaJ70mUUvEUEBLJ4JHYj+qZ0FHK2zCCRlNEHWtVGR/+D8tNZYJg8 XrMQ== X-Gm-Message-State: AOAM53343tOuug9TG7S6eQVs0xK8CQgnQ+olcVp0iKH29tPaF0iub11R dRJb6bggQBOhrxr3SMN60fR6zg== X-Google-Smtp-Source: ABdhPJxUkcP7tvQC/1g/mrtlDB25tdXfgU7PSiuLoapLSdk12hfg/ro1vp1kr0Y7TNymzUpLM79pKg== X-Received: by 2002:a7b:c4c5:: with SMTP id g5mr19646400wmk.139.1643663207885; Mon, 31 Jan 2022 13:06:47 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id b11sm314961wmq.46.2022.01.31.13.06.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jan 2022 13:06:47 -0800 (PST) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , linux-fbdev@vger.kernel.org, LKML , Daniel Vetter , Daniel Vetter , Daniel Vetter , Claudio Suarez , Tetsuo Handa , Thomas Zimmermann , Greg Kroah-Hartman , Du Cheng , Sam Ravnborg , Matthew Wilcox , William Kucharski , Alex Deucher , Zheyu Ma , Zhen Lei , Xiyu Yang Subject: [PATCH 14/21] fbcon: use lock_fb_info in fbcon_open/release Date: Mon, 31 Jan 2022 22:05:45 +0100 Message-Id: <20220131210552.482606-15-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20220131210552.482606-1-daniel.vetter@ffwll.ch> References: <20220131210552.482606-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Now we get to the real motiviation, because fbmem.c insists that that's the right lock for these. Ofc fbcon.c has a lot more places where it probably should call lock_fb_info(). But looking at fbmem.c at least most of these seem to be protected by console_lock() too, which is probably what papers over any issues. Note that this means we're shuffling around a bit the locking sections for some of the console takeover and unbind paths, but not all: - console binding/unbinding from the console layer never with lock_fb_info - unbind (as opposed to unlink) never bother with lock_fb_info Also the real serialization against set_par and set_pan are still doing by wrapping the entire ioctl code in console_lock(). So this shuffling shouldn't be worse than what we had from a "can you trigger races?" pov, but it's at least clearer. Signed-off-by: Daniel Vetter Cc: Daniel Vetter Cc: Claudio Suarez Cc: Tetsuo Handa Cc: Thomas Zimmermann Cc: Greg Kroah-Hartman Cc: Du Cheng Cc: Sam Ravnborg Cc: Matthew Wilcox Cc: William Kucharski Cc: Alex Deucher Cc: Zheyu Ma Cc: Zhen Lei Cc: Xiyu Yang Acked-by: Sam Ravnborg --- drivers/video/fbdev/core/fbcon.c | 5 +++++ drivers/video/fbdev/core/fbmem.c | 4 ---- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 5a3391ff038d..496bc5f2133e 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -682,8 +682,10 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount) static void fbcon_release(struct fb_info *info) { + lock_fb_info(info); if (info->fbops->fb_release) info->fbops->fb_release(info, 0); + unlock_fb_info(info); module_put(info->fbops->owner); } @@ -695,11 +697,14 @@ static int fbcon_open(struct fb_info *info) if (!try_module_get(info->fbops->owner)) return -ENODEV; + lock_fb_info(info); if (info->fbops->fb_open && info->fbops->fb_open(info, 0)) { + unlock_fb_info(info); module_put(info->fbops->owner); return -ENODEV; } + unlock_fb_info(info); ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL); if (!ops) { diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 0fa7ede94fa6..fd51d12f2702 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1653,9 +1653,7 @@ static int do_register_framebuffer(struct fb_info *fb_info) console_lock(); else atomic_inc(&ignore_console_lock_warning); - lock_fb_info(fb_info); ret = fbcon_fb_registered(fb_info); - unlock_fb_info(fb_info); if (!lockless_register_fb) console_unlock(); @@ -1672,9 +1670,7 @@ static void unbind_console(struct fb_info *fb_info) return; console_lock(); - lock_fb_info(fb_info); fbcon_fb_unbind(fb_info); - unlock_fb_info(fb_info); console_unlock(); }