From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: [PATCH V33 21/30] x86/mmiotrace: Lock down the testmmiotrace module Date: Thu, 20 Jun 2019 18:19:32 -0700 Message-ID: <20190621011941.186255-22-matthewgarrett@google.com> References: <20190621011941.186255-1-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190621011941.186255-1-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org To: jmorris@namei.org Cc: linux-security@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells , Thomas Gleixner , Matthew Garrett , Steven Rostedt , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org List-Id: linux-api@vger.kernel.org From: David Howells The testmmiotrace module shouldn't be permitted when the kernel is locked down as it can be used to arbitrarily read and write MMIO space. This is a runtime check rather than buildtime in order to allow configurations where the same kernel may be run in both locked down or permissive modes depending on local policy. Suggested-by: Thomas Gleixner Signed-off-by: David Howells cc: Thomas Gleixner cc: Steven Rostedt cc: Ingo Molnar cc: "H. Peter Anvin" cc: x86@kernel.org --- arch/x86/mm/testmmiotrace.c | 3 +++ include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 5 insertions(+) diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c index f6ae6830b341..a6b204f9f505 100644 --- a/arch/x86/mm/testmmiotrace.c +++ b/arch/x86/mm/testmmiotrace.c @@ -115,6 +115,9 @@ static int __init init(void) { unsigned long size = (read_far) ? (8 << 20) : (16 << 10); + if (security_is_locked_down(LOCKDOWN_MMIOTRACE)) + return -EPERM; + if (mmio_address == 0) { pr_err("you have to use the module argument mmio_address.\n"); pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n"); diff --git a/include/linux/security.h b/include/linux/security.h index 47ca04ac00f6..89b7adfae525 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -93,6 +93,7 @@ enum lockdown_reason { LOCKDOWN_PCMCIA_CIS, LOCKDOWN_TIOCSSERIAL, LOCKDOWN_MODULE_PARAMETERS, + LOCKDOWN_MMIOTRACE, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 0788d4805449..215615e67237 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -29,6 +29,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage", [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO", [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters", + [LOCKDOWN_MMIOTRACE] = "unsafe mmio", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog