From patchwork Thu Jun 10 21:43:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnd Bergmann X-Patchwork-Id: 12314029 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22D6BC48BD1 for ; Thu, 10 Jun 2021 21:45:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E57D613F1 for ; Thu, 10 Jun 2021 21:45:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230450AbhFJVqz (ORCPT ); Thu, 10 Jun 2021 17:46:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:54110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230392AbhFJVqy (ORCPT ); Thu, 10 Jun 2021 17:46:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0DD076141F; Thu, 10 Jun 2021 21:44:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623361497; bh=TlkIF8TF9j+74Su5L9XU65cloJswG8lpwGpXJ4LchNY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gE3YkI5pig+tAXh2h7gzE91McLRugMNmNlrUFvaPe+iucAOmqFR6HSlBJ6wokc8+f cFZPflPhIuQ8BhClViCzjX0neTGcVQtuxHwe9AcEqBXad4zFmhNN7wy1zL/Cw6Lbrq errKk8gIyoAezLRNep+f0GXJY/OOg/+YKmBZ5TUkWgxxYc0XsdQ5CLH012nCxfRX0o kYxgB/YVDCrljBIOGpkiRhLU/KU3KAkyyKsuTkphUY8hED6x5U/2TuwDw/cyAq9ou8 6L7+z6KoKrJ7q0BzrFxEuCHEw0MqQK1slxv7pB6sZSFWGcoxg81sQfhcgDOTMja1fe kw6t9zTzvBfEw== From: Arnd Bergmann To: Hans Verkuil , Mauro Carvalho Chehab Cc: Arnd Bergmann , "Lad, Prabhakar" , Eduardo Valentin , Sakari Ailus , Greg Kroah-Hartman , Vaibhav Gupta , Liu Shixin , Laurent Pinchart , Jacopo Mondi , Andy Shevchenko , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-staging@lists.linux.dev Subject: [PATCH v2 2/7] media: v4l2-core: explicitly clear ioctl input data Date: Thu, 10 Jun 2021 23:43:00 +0200 Message-Id: <20210610214305.4170835-3-arnd@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210610214305.4170835-1-arnd@kernel.org> References: <20210610214305.4170835-1-arnd@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org From: Arnd Bergmann As seen from a recent syzbot bug report, mistakes in the compat ioctl implementation can lead to uninitialized kernel stack data getting used as input for driver ioctl handlers. The reported bug is now fixed, but it's possible that other related bugs are still present or get added in the future. As the drivers need to check user input already, the possible impact is fairly low, but it might still cause an information leak. To be on the safe side, always clear the entire ioctl buffer before calling the conversion handler functions that are meant to initialize them. Signed-off-by: Arnd Bergmann --- drivers/media/v4l2-core/v4l2-ioctl.c | 51 ++++++++++++++++------------ 1 file changed, 29 insertions(+), 22 deletions(-) diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c index 58df927aec7e..bf5eb07296a5 100644 --- a/drivers/media/v4l2-core/v4l2-ioctl.c +++ b/drivers/media/v4l2-core/v4l2-ioctl.c @@ -3122,12 +3122,23 @@ static int video_get_user(void __user *arg, void *parg, if (cmd == real_cmd) { if (copy_from_user(parg, (void __user *)arg, n)) - err = -EFAULT; - } else if (in_compat_syscall()) { - err = v4l2_compat_get_user(arg, parg, cmd); - } else { - switch (cmd) { + return -EFAULT; + + /* zero out anything we don't copy from userspace */ + if (n < _IOC_SIZE(real_cmd)) + memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); + + return 0; + } + + /* zero out whole buffer first to deal with missing emulation */ + memset(parg, 0, _IOC_SIZE(real_cmd)); + + if (in_compat_syscall()) + return v4l2_compat_get_user(arg, parg, cmd); + #if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) + switch (cmd) { case VIDIOC_QUERYBUF_TIME32: case VIDIOC_QBUF_TIME32: case VIDIOC_DQBUF_TIME32: @@ -3140,28 +3151,24 @@ static int video_get_user(void __user *arg, void *parg, *vb = (struct v4l2_buffer) { .index = vb32.index, - .type = vb32.type, - .bytesused = vb32.bytesused, - .flags = vb32.flags, - .field = vb32.field, - .timestamp.tv_sec = vb32.timestamp.tv_sec, - .timestamp.tv_usec = vb32.timestamp.tv_usec, - .timecode = vb32.timecode, - .sequence = vb32.sequence, - .memory = vb32.memory, - .m.userptr = vb32.m.userptr, - .length = vb32.length, - .request_fd = vb32.request_fd, + .type = vb32.type, + .bytesused = vb32.bytesused, + .flags = vb32.flags, + .field = vb32.field, + .timestamp.tv_sec = vb32.timestamp.tv_sec, + .timestamp.tv_usec = vb32.timestamp.tv_usec, + .timecode = vb32.timecode, + .sequence = vb32.sequence, + .memory = vb32.memory, + .m.userptr = vb32.m.userptr, + .length = vb32.length, + .request_fd = vb32.request_fd, }; break; } -#endif - } } +#endif - /* zero out anything we don't copy from userspace */ - if (!err && n < _IOC_SIZE(real_cmd)) - memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); return err; }