From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out01.mta.xmission.com ([166.70.13.231]:36834 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003AbeFET4k (ORCPT ); Tue, 5 Jun 2018 15:56:40 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Ilya Matveychikov Cc: linux-kernel@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org References: Date: Tue, 05 Jun 2018 14:56:31 -0500 In-Reply-To: (Ilya Matveychikov's message of "Tue, 5 Jun 2018 10:59:51 +0400") Message-ID: <87o9gpatxs.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Subject: Re: [PATCH] ksys_mount: check for permissions before resource allocation Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Ilya Matveychikov writes: > Just CC’ed to some of maintainers. > > $ perl scripts/get_maintainer.pl fs/0001-ksys_mount-check-for-permissions-before-resource-all.patch > Alexander Viro (maintainer:FILESYSTEMS (VFS and infrastructure)) > linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and infrastructure)) > linux-kernel@vger.kernel.org (open list) > >> On Jun 5, 2018, at 6:00 AM, Ilya Matveychikov wrote: >> >> Early check for mount permissions prevents possible allocation of 3 >> pages from kmalloc() pool by unpriveledged user which can be used for >> spraying the kernel heap. *Snort* You clearly have not read may_mount. Your modified code still let's unprivileged users in. So even if all of Al's good objections were not applicable this change would still be buggy and wrong. Nacked-by: "Eric W. Biederman" >> Signed-off-by: Ilya V. Matveychikov >> --- >> fs/namespace.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/fs/namespace.c b/fs/namespace.c >> index 5f75969adff1..1ef8feb2de2a 100644 >> --- a/fs/namespace.c >> +++ b/fs/namespace.c >> @@ -3046,6 +3046,9 @@ int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type, >> char *kernel_dev; >> void *options; >> >> + if (!may_mount()) >> + return -EPERM; >> + >> kernel_type = copy_mount_string(type); >> ret = PTR_ERR(kernel_type); >> if (IS_ERR(kernel_type)) >> -- >> 2.17.0 >>