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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id t4sm15192866pgj.20.2019.06.22.17.04.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 22 Jun 2019 17:04:32 -0700 (PDT) Date: Sat, 22 Jun 2019 17:04:32 -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 V34 20/29] x86/mmiotrace: Lock down the testmmiotrace module Message-ID: <201906221704.495671B@keescook> References: <20190622000358.19895-1-matthewgarrett@google.com> <20190622000358.19895-21-matthewgarrett@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190622000358.19895-21-matthewgarrett@google.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Jun 21, 2019 at 05:03:49PM -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 > 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 f6ae6830b341..6b9486baa2e9 100644 > --- a/arch/x86/mm/testmmiotrace.c > +++ b/arch/x86/mm/testmmiotrace.c > @@ -7,6 +7,7 @@ > #include > #include > #include > +#include > > static unsigned long mmio_address; > module_param_hw(mmio_address, ulong, iomem, 0); > @@ -114,6 +115,10 @@ 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 88064d7f6827..c649cb91e762 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 d03c4c296af7..cd86ed9f4d4b 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 > -- Kees Cook