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 B90F0C00140 for ; Fri, 5 Aug 2022 06:22:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234911AbiHEGWO convert rfc822-to-8bit (ORCPT ); Fri, 5 Aug 2022 02:22:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230492AbiHEGWN (ORCPT ); Fri, 5 Aug 2022 02:22:13 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD47A5A2EC for ; Thu, 4 Aug 2022 23:22:09 -0700 (PDT) Received: from kwepemi100011.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Lzb5y2QLtzlVsG; Fri, 5 Aug 2022 14:19:18 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by kwepemi100011.china.huawei.com (7.221.188.134) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 5 Aug 2022 14:22:03 +0800 Received: from dggpemm500006.china.huawei.com ([7.185.36.236]) by dggpemm500006.china.huawei.com ([7.185.36.236]) with mapi id 15.01.2375.024; Fri, 5 Aug 2022 14:22:03 +0800 From: "chenjun (AM)" To: Cengiz Can , "stable@vger.kernel.org" , "deller@gmx.de" , "geert@linux-m68k.org" , "b.zolnierkie@samsung.com" , "gregkh@linuxfoundation.org" CC: "xuqiang (M)" Subject: Re: [PATCH stable 4.14 v3 2/3] fbcon: Prevent that screen size is smaller than font size Thread-Topic: [PATCH stable 4.14 v3 2/3] fbcon: Prevent that screen size is smaller than font size Thread-Index: AQHYqJHevjk/Lf6Xg0CLiLdyiY6P+Q== Date: Fri, 5 Aug 2022 06:22:03 +0000 Message-ID: References: <20220804122734.121201-1-chenjun102@huawei.com> <20220804122734.121201-3-chenjun102@huawei.com> <602ce75b5b6dba51bc24cace86c1ada27fb6b0e9.camel@canonical.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.174.178.43] Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 在 2022/8/5 14:09, Cengiz Can 写道: > On Thu, 2022-08-04 at 12:27 +0000, Chen Jun wrote: >> 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 >> [Chen Jun: 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); > > Why do we lock and unlock here consecutively? > > Can it be a leftover? > > Because in upstream commit, lock encapsulates `fb_set_var`, > `fbcon_modechange_possible` and `fbcon_update_vcs` calls, which makes > sense. > > Here, it doesn't. > Thanks, lock_fb_info(info) is wrong here. >> 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 */ > > -- Regards Chen Jun