From patchwork Tue Aug 20 00:17:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11102371 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8F6D91395 for ; Tue, 20 Aug 2019 00:18:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6FAD922CF8 for ; Tue, 20 Aug 2019 00:18:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="DnG3SLg+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728929AbfHTASY (ORCPT ); Mon, 19 Aug 2019 20:18:24 -0400 Received: from mail-pf1-f201.google.com ([209.85.210.201]:33355 "EHLO mail-pf1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728927AbfHTASY (ORCPT ); Mon, 19 Aug 2019 20:18:24 -0400 Received: by mail-pf1-f201.google.com with SMTP id r130so3533189pfc.0 for ; Mon, 19 Aug 2019 17:18:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=KEN1/621HMw7IMfp8Bhrbn/lMKb+FMpWN6y+R4B0zXU=; b=DnG3SLg+kryCv883pYqzrppk2z/DgKjwrD4Sghbocds356yt5bJDzjzQb1b+wveJDe 1H79mW4g8luPWRTilF0N4iZ/U7F+W91vu3dXhCdCQZhqRx8+sFVTXbiFHFTKZXAewmB5 46PiuAXySCSkliboNVn6zkBBwNsW0UkhHmUeR9+fwM4rBk4oq1wE2NCml1IQEsdPUxPj U8LftEt/jHOXe4DBSa4/VkbXgiMCFwq7AKbR5NVsLcT/uwzf2vvmZh83OgT0RNRBc7bZ V+ksZ0m0vn8rJUbVwZF0XuOrBWK7HDBzHHS38G68udbIipnGCbofxTBqMxOTRP4yP8Vn uH8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=KEN1/621HMw7IMfp8Bhrbn/lMKb+FMpWN6y+R4B0zXU=; b=ozdXAt9OftndEq0bhEceJFI5e1XjNhVF2LFmUXMCD4pDwKF9CZxLdBkzg3nxz7bkD+ xxN43UFjFnDMKdb6NLsNpJxvjTnRUbck9AEhcsazsrTCxHDBYYQtmXJasXGUspaEWVn9 1u0RWWpzsUIRHyd4Gbo2ULMGrlF56mzB7zkz7NmV/zBW0rqYhzOVFd1z5Fi7LjMv+WOZ lY/yFR0cUFd8e8t0P07mADgUpUQ0JDFIXzQxcPlk7SF5EC4T+YlovXGh+nGiqTGJ7Dp7 RoJyqrSai5SyS5mLFtVGC8KrGSF5qVkDmISZXilScHnTwwLo30tqsBDJzVrQkfIVLGOC G9Iw== X-Gm-Message-State: APjAAAVJqrKIw/JXPKzNOAizxS+fekW8CZWLNEDA3rNCZbomNV7ZWTKL xij1F2mvGywp3vUB2CHKyvI7yfk6rYrfCBf388uR7w== X-Google-Smtp-Source: APXvYqzu5BEv2mtJKqJd6UcBWYswLbyp2Wvqob1sMe+SQF24ZfScjj7xKDwMAvtmGOpUZt7gdkbtAJE2Vkut4H1ejF1s9A== X-Received: by 2002:a63:9e56:: with SMTP id r22mr22292240pgo.221.1566260303010; Mon, 19 Aug 2019 17:18:23 -0700 (PDT) Date: Mon, 19 Aug 2019 17:17:41 -0700 In-Reply-To: <20190820001805.241928-1-matthewgarrett@google.com> Message-Id: <20190820001805.241928-6-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190820001805.241928-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.23.0.rc1.153.gdeed80330f-goog Subject: [PATCH V40 05/29] lockdown: Restrict /dev/{mem,kmem,port} when the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , David Howells , Matthew Garrett , Kees Cook , x86@kernel.org Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: Matthew Garrett Allowing users to read and write to core kernel memory makes it possible for the kernel to be subverted, avoiding module loading restrictions, and also to steal cryptographic information. Disallow /dev/mem and /dev/kmem from being opened this when the kernel has been locked down to prevent this. Also disallow /dev/port from being opened to prevent raw ioport access and thus DMA from being used to accomplish the same thing. Signed-off-by: David Howells Signed-off-by: Matthew Garrett Reviewed-by: Kees Cook Cc: x86@kernel.org Signed-off-by: James Morris --- drivers/char/mem.c | 7 +++++-- include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index b08dc50f9f26..d0148aee1aab 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -29,8 +29,8 @@ #include #include #include - #include +#include #ifdef CONFIG_IA64 # include @@ -786,7 +786,10 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) static int open_port(struct inode *inode, struct file *filp) { - return capable(CAP_SYS_RAWIO) ? 0 : -EPERM; + if (!capable(CAP_SYS_RAWIO)) + return -EPERM; + + return security_locked_down(LOCKDOWN_DEV_MEM); } #define zero_lseek null_lseek diff --git a/include/linux/security.h b/include/linux/security.h index 9e8abb60a99f..e5dd446ef35b 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -104,6 +104,7 @@ enum lsm_event { enum lockdown_reason { LOCKDOWN_NONE, LOCKDOWN_MODULE_SIGNATURE, + LOCKDOWN_DEV_MEM, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index d8e42125a5dd..240ecaa10a1d 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -19,6 +19,7 @@ static enum lockdown_reason kernel_locked_down; static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", + [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };