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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id 23sm31483030pfn.176.2019.07.18.14.06.24 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 18 Jul 2019 14:06:24 -0700 (PDT) Date: Thu, 18 Jul 2019 14:06:23 -0700 From: Kees Cook To: Matthew Garrett Cc: jmorris@namei.org, linux-security-module@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 Subject: Re: [PATCH V36 20/29] x86/mmiotrace: Lock down the testmmiotrace module Message-ID: <201907181406.0E364D490@keescook> References: <20190718194415.108476-1-matthewgarrett@google.com> <20190718194415.108476-21-matthewgarrett@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190718194415.108476-21-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 18, 2019 at 12:44:06PM -0700, Matthew Garrett wrote: > 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 -Kees > Signed-off-by: Matthew Garrett > Acked-by: Steven Rostedt (VMware) > cc: Thomas Gleixner > cc: Steven Rostedt > cc: Ingo Molnar > cc: "H. Peter Anvin" > cc: x86@kernel.org > --- > arch/x86/mm/testmmiotrace.c | 5 +++++ > include/linux/security.h | 1 + > security/lockdown/lockdown.c | 1 + > 3 files changed, 7 insertions(+) > > diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c > index 0881e1ff1e58..a8bd952e136d 100644 > --- a/arch/x86/mm/testmmiotrace.c > +++ b/arch/x86/mm/testmmiotrace.c > @@ -8,6 +8,7 @@ > #include > #include > #include > +#include > > static unsigned long mmio_address; > module_param_hw(mmio_address, ulong, iomem, 0); > @@ -115,6 +116,10 @@ static void do_test_bulk_ioremapping(void) > static int __init init(void) > { > unsigned long size = (read_far) ? (8 << 20) : (16 << 10); > + int ret = security_locked_down(LOCKDOWN_MMIOTRACE); > + > + if (ret) > + return ret; > > if (mmio_address == 0) { > pr_err("you have to use the module argument mmio_address.\n"); > diff --git a/include/linux/security.h b/include/linux/security.h > index 43fa3486522b..3f7b6a4cd65a 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -114,6 +114,7 @@ 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 5177938cfa0d..37b7d7e50474 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", > }; > -- > 2.22.0.510.g264f2c817a-goog > -- Kees Cook