From patchwork Wed Sep 25 05:29:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qianqiang Liu X-Patchwork-Id: 13811614 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.2]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AB8AF14A62F; Wed, 25 Sep 2024 05:29:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.2 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727242202; cv=none; b=YitBfq703jsaB3omdE+ZZbt4VAEmsceXWYLq9tFNSgJv5qdLK/9zjSu90HH7GUr7XAVBxaiR1x2J2o7TbuGKznUfIK+7tLZQ0UEXQqkh6PrSB8UycFn5IbD/0kmwFepkiX+MBOSkFVzOz/uDNXLFVUjDiIKmAFf4V2PPPYdL7lc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727242202; c=relaxed/simple; bh=jGpqJbVzRpKzy5QsoMynmjUtdDYVRQ+bX/xMcnAWlUw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QA8DKZ6bM0SlrdrOwinQ7rXjHVBFo1Q3BKLdyjk79HmVm/yixI6mxRojW2vO5dATe3mjHZnFELIxjd9QY9PkR78+cqRAVCnbDCkiQvjN+w0HTW7Q/HCmVx+g4ZcVlu3NkigAOsTiGgWE5UOMIduYxEAjboSPxkGaWgigDzHIbb0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=WkKDmf+i; arc=none smtp.client-ip=220.197.31.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="WkKDmf+i" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version: Content-Type; bh=aqkoSnEgaj9DVcjWERksyIfsDRhiR+luevjNipHPwIo=; b=WkKDmf+iFDYdvla8K6TRmY4PJxkiiKAgpydWfGjqsQvAclMl9q0/MehBHbG608 8NVPjwLY+uwMzyoZgCep4glrcOlK+X94WxQosk9jbvB563JaYLZaAv6zBMb8Drjk dDLRg1pJoNAlchuKGPFMWbmC1XzGsfvk/TubUu9WUKEgs= Received: from localhost (unknown [60.168.209.67]) by gzsmtp2 (Coremail) with SMTP id sSgvCgAXg_7An_NmfUNVAA--.16028S2; Wed, 25 Sep 2024 13:29:37 +0800 (CST) Date: Wed, 25 Sep 2024 13:29:36 +0800 From: Qianqiang Liu To: Helge Deller Cc: linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Subject: [PATCH v3] fbcon: Fix a NULL pointer dereference issue in fbcon_putcs Message-ID: References: <20240916011027.303875-1-qianqiang.liu@163.com> <1b1a2d3c-ed4a-4d9b-b87a-8d05f3d6592e@gmx.de> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1b1a2d3c-ed4a-4d9b-b87a-8d05f3d6592e@gmx.de> X-CM-TRANSID: sSgvCgAXg_7An_NmfUNVAA--.16028S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7AF17Jw4xJw1xJryDur1ftFb_yoW8uFykpF W5tFWaqrZ8try3Z34jgr4xZr1rXas8ArWUWayFqa4fZFnFvF18WFyIgryUCrWru3W0kryx KF1jy3y2kas3WaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jEdgAUUUUU= X-CM-SenderInfo: xtld01pldqwhxolxqiywtou0bp/1tbiLxtlambzkrb51AAAsn syzbot has found a NULL pointer dereference bug in fbcon. Here is the simplified C reproducer: struct param { uint8_t type; struct tiocl_selection ts; }; int main() { struct fb_con2fbmap con2fb; struct param param; int fd = open("/dev/fb1", 0, 0); con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0; int fd1 = open("/dev/tty1", O_RDWR, 0); ioctl(fd1, TIOCLINUX, ¶m); con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); return 0; } After calling ioctl(fd1, TIOCLINUX, ¶m), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) causes the kernel to follow a different execution path: set_con2fb_map -> con2fb_init_display -> fbcon_set_disp -> redraw_screen -> hide_cursor -> clear_selection -> highlight -> invert_screen -> do_update_region -> fbcon_putcs -> ops->putcs Since ops->putcs is a NULL pointer, this leads to a kernel panic. To prevent this, we need to call set_blitting_type() within set_con2fb_map() to properly initialize ops->putcs. Reported-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3d613ae53c031502687a Tested-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Signed-off-by: Qianqiang Liu --- Changes since v2: - Document the commit message in more detail --- Changes since v1: - Initialize ops->putcs by calling set_blitting_type() --- drivers/video/fbdev/core/fbcon.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 2e093535884b..d9abae2516d8 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -861,6 +861,8 @@ static int set_con2fb_map(int unit, int newidx, int user) return err; fbcon_add_cursor_work(info); + } else if (vc) { + set_blitting_type(vc, info); } con2fb_map[unit] = newidx;