From: David Howells <dhowells@xxxxxxxxxx>
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 <tglx@xxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx
Signed-off-by: Matthew Garrett <mjg59@xxxxxxxxxx>
cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
cc: Ingo Molnar <mingo@xxxxxxxxxx>
cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
cc: x86@xxxxxxxxxx
---
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
