Re: [PATCH V34 20/29] x86/mmiotrace: Lock down the testmmiotrace module
From: Kees Cook <hidden>
Date: 2019-06-23 00:04:36
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linux-api, lkml
On Fri, Jun 21, 2019 at 05:03:49PM -0700, Matthew Garrett wrote:
From: David Howells <dhowells@redhat.com> 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 <redacted> Signed-off-by: David Howells <dhowells@redhat.com
Reviewed-by: Kees Cook <redacted> -Kees
quoted hunk ↗ jump to hunk
Signed-off-by: Matthew Garrett <redacted> cc: Thomas Gleixner <redacted> cc: Steven Rostedt <rostedt@goodmis.org> cc: Ingo Molnar <mingo@kernel.org> cc: "H. Peter Anvin" <hpa@zytor.com> 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 <linux/module.h> #include <linux/io.h> #include <linux/mmiotrace.h> +#include <linux/security.h> 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