[PATCH V40 12/29] x86: Lock down IO port access when the kernel is locked down
From: Matthew Garrett <hidden>
Date: 2019-08-20 00:18:45
Also in:
linux-security-module, lkml
Subsystem:
lockdown security module, security subsystem, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Nicolas Bouchinet, Xiu Jianfeng, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Matthew Garrett <mjg59@srcf.ucam.org> IO port access would permit users to gain access to PCI configuration registers, which in turn (on a lot of hardware) give access to MMIO register space. This would potentially permit root to trigger arbitrary DMA, so lock it down by default. This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and KDDISABIO console ioctls. Signed-off-by: Matthew Garrett <redacted> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Kees Cook <redacted> cc: x86@kernel.org Signed-off-by: James Morris <jmorris@namei.org> --- arch/x86/kernel/ioport.c | 7 +++++-- include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 0fe1c8782208..61a89d3c0382 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c@@ -11,6 +11,7 @@ #include <linux/errno.h> #include <linux/types.h> #include <linux/ioport.h> +#include <linux/security.h> #include <linux/smp.h> #include <linux/stddef.h> #include <linux/slab.h>
@@ -31,7 +32,8 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) return -EINVAL; - if (turn_on && !capable(CAP_SYS_RAWIO)) + if (turn_on && (!capable(CAP_SYS_RAWIO) || + security_locked_down(LOCKDOWN_IOPORT))) return -EPERM; /*
@@ -126,7 +128,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level) return -EINVAL; /* Trying to gain more privileges? */ if (level > old) { - if (!capable(CAP_SYS_RAWIO)) + if (!capable(CAP_SYS_RAWIO) || + security_locked_down(LOCKDOWN_IOPORT)) return -EPERM; } regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/include/linux/security.h b/include/linux/security.h
index 2b763f0ee352..cd93fa5d3c6d 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h@@ -108,6 +108,7 @@ enum lockdown_reason { LOCKDOWN_KEXEC, LOCKDOWN_HIBERNATION, LOCKDOWN_PCI_ACCESS, + LOCKDOWN_IOPORT, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, };
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 410e90eda848..8b7d65dbb086 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c@@ -23,6 +23,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_KEXEC] = "kexec of unsigned images", [LOCKDOWN_HIBERNATION] = "hibernation", [LOCKDOWN_PCI_ACCESS] = "direct PCI access", + [LOCKDOWN_IOPORT] = "raw io port access", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };
--
2.23.0.rc1.153.gdeed80330f-goog