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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 490B2C19F2B for ; Thu, 4 Aug 2022 11:18:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231637AbiHDLSd (ORCPT ); Thu, 4 Aug 2022 07:18:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239670AbiHDLSQ (ORCPT ); Thu, 4 Aug 2022 07:18:16 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6290D66127 for ; Thu, 4 Aug 2022 04:18:07 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Lz5hX1kClzWfD2; Thu, 4 Aug 2022 19:14:04 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 4 Aug 2022 19:18:00 +0800 Received: from mdc.huawei.com (10.175.112.208) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 4 Aug 2022 19:18:00 +0800 From: Chen Jun To: , , , , CC: Subject: [PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size Date: Thu, 4 Aug 2022 11:15:38 +0000 Message-ID: <20220804111539.96424-3-chenjun102@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220804111539.96424-1-chenjun102@huawei.com> References: <20220804111539.96424-1-chenjun102@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.112.208] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Helge Deller commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream We need to prevent that users configure a screen size which is smaller than the currently selected font size. Otherwise rendering chars on the screen will access memory outside the graphics memory region. This patch adds a new function fbcon_modechange_possible() which implements this check and which later may be extended with other checks if necessary. The new function is called from the FBIOPUT_VSCREENINFO ioctl handler in fbmem.c, which will return -EINVAL if userspace asked for a too small screen size. Signed-off-by: Helge Deller Reviewed-by: Geert Uytterhoeven Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/ [sudip: adjust context] Signed-off-by: Chen Jun --- drivers/video/fbdev/core/fbcon.c | 28 ++++++++++++++++++++++++++++ drivers/video/fbdev/core/fbmem.c | 10 +++++++--- include/linux/fbcon.h | 4 ++++ 3 files changed, 39 insertions(+), 3 deletions(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index a97e94b1c84f..b84264e98929 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2706,6 +2706,34 @@ static void fbcon_set_all_vcs(struct fb_info *info) fbcon_modechanged(info); } +/* let fbcon check if it supports a new screen resolution */ +int fbcon_modechange_possible(struct fb_info *info, struct fb_var_screeninfo *var) +{ + struct fbcon_ops *ops = info->fbcon_par; + struct vc_data *vc; + unsigned int i; + + WARN_CONSOLE_UNLOCKED(); + + if (!ops) + return 0; + + /* prevent setting a screen size which is smaller than font size */ + for (i = first_fb_vc; i <= last_fb_vc; i++) { + vc = vc_cons[i].d; + if (!vc || vc->vc_mode != KD_TEXT || + registered_fb[con2fb_map[i]] != info) + continue; + + if (vc->vc_font.width > FBCON_SWAP(var->rotate, var->xres, var->yres) || + vc->vc_font.height > FBCON_SWAP(var->rotate, var->yres, var->xres)) + return -EINVAL; + } + + return 0; +} +EXPORT_SYMBOL_GPL(fbcon_modechange_possible); + static int fbcon_mode_deleted(struct fb_info *info, struct fb_videomode *mode) { diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 9087d467cc46..264e8ca5efa7 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1134,9 +1134,13 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, console_unlock(); return -ENODEV; } - info->flags |= FBINFO_MISC_USEREVENT; - ret = fb_set_var(info, &var); - info->flags &= ~FBINFO_MISC_USEREVENT; + ret = fbcon_modechange_possible(info, &var); + if (!ret) { + info->flags |= FBINFO_MISC_USEREVENT; + ret = fb_set_var(info, &var); + info->flags &= ~FBINFO_MISC_USEREVENT; + } + lock_fb_info(info); unlock_fb_info(info); console_unlock(); if (!ret && copy_to_user(argp, &var, sizeof(var))) diff --git a/include/linux/fbcon.h b/include/linux/fbcon.h index f68a7db14165..39939d55c834 100644 --- a/include/linux/fbcon.h +++ b/include/linux/fbcon.h @@ -4,9 +4,13 @@ #ifdef CONFIG_FRAMEBUFFER_CONSOLE void __init fb_console_init(void); void __exit fb_console_exit(void); +int fbcon_modechange_possible(struct fb_info *info, + struct fb_var_screeninfo *var); #else static inline void fb_console_init(void) {} static inline void fb_console_exit(void) {} +static inline int fbcon_modechange_possible(struct fb_info *info, + struct fb_var_screeninfo *var) { return 0; } #endif #endif /* _LINUX_FBCON_H */ -- 2.17.1