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Revision 5f56a74cc0a6d9b9f8ba89cea29cd7c4774cb2b1 authored by Ard Biesheuvel on 20 September 2022, 15:08:23 UTC, committed by Ard Biesheuvel on 22 September 2022, 08:15:44 UTC 
efi: libstub: check Shim mode using MokSBStateRT
 
We currently check the MokSBState variable to decide whether we should
treat UEFI secure boot as being disabled, even if the firmware thinks
otherwise. This is used by shim to indicate that it is not checking
signatures on boot images. In the kernel, we use this to relax lockdown
policies.

However, in cases where shim is not even being used, we don't want this
variable to interfere with lockdown, given that the variable may be
non-volatile and therefore persist across a reboot. This means setting
it once will persistently disable lockdown checks on a given system.

So switch to the mirrored version of this variable, called MokSBStateRT,
which is supposed to be volatile, and this is something we can check.

Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Peter Jones <pjones@redhat.com>
1 parent 63bf28c
Raw File
ioremap.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * Re-map IO memory to kernel address space so that we can access it.
 * This is needed for high PCI addresses that aren't mapped in the
 * 640k-1MB IO memory area on PC's
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 */
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/export.h>

void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
			   unsigned long prot)
{
	unsigned long offset, vaddr;
	phys_addr_t last_addr;
	struct vm_struct *area;

	/* Disallow wrap-around or zero size */
	last_addr = phys_addr + size - 1;
	if (!size || last_addr < phys_addr)
		return NULL;

	/* Page-align mappings */
	offset = phys_addr & (~PAGE_MASK);
	phys_addr -= offset;
	size = PAGE_ALIGN(size + offset);

	if (!ioremap_allowed(phys_addr, size, prot))
		return NULL;

	area = get_vm_area_caller(size, VM_IOREMAP,
			__builtin_return_address(0));
	if (!area)
		return NULL;
	vaddr = (unsigned long)area->addr;
	area->phys_addr = phys_addr;

	if (ioremap_page_range(vaddr, vaddr + size, phys_addr,
			       __pgprot(prot))) {
		free_vm_area(area);
		return NULL;
	}

	return (void __iomem *)(vaddr + offset);
}
EXPORT_SYMBOL(ioremap_prot);

void iounmap(volatile void __iomem *addr)
{
	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);

	if (!iounmap_allowed(vaddr))
		return;

	if (is_vmalloc_addr(vaddr))
		vunmap(vaddr);
}
EXPORT_SYMBOL(iounmap);
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