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x86: Lock down IO port access when the kernel is locked down 

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 <mjg59@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: x86@kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Matthew Garrett 2019-08-19 17:17:48 -07:00 committed by James Morris
parent eb627e1772
commit 96c4f67293
3 changed files with 7 additions and 2 deletions
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7
arch/x86/kernel/ioport.c
View File

@ -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) |

1
include/linux/security.h
View File

@ -108,6 +108,7 @@ enum lockdown_reason {
LOCKDOWN_KEXEC,
LOCKDOWN_HIBERNATION,
LOCKDOWN_PCI_ACCESS,
LOCKDOWN_IOPORT,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

1
security/lockdown/lockdown.c
View File

@ -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",
};