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arm64: efi: Limit allocations to 48-bit addressable physical region 

The UEFI spec does not mention or reason about the configured size of
the virtual address space at all, but it does mention that all memory
should be identity mapped using a page size of 4 KiB.

This means that a LPA2 capable system that has any system memory outside
of the 48-bit addressable physical range and follows the spec to the
letter may serve page allocation requests from regions of memory that
the kernel cannot access unless it was built with LPA2 support and
enables it at runtime.

So let's ensure that all page allocations are limited to the 48-bit
range.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Ard Biesheuvel 2022-12-05 09:10:17 +01:00
parent d9f26ae731
commit a37dac5c5d
6 changed files with 13 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/include/asm/efi.h
View File

@ -92,6 +92,7 @@ static inline unsigned long efi_get_kimg_min_align(void)
}
#define EFI_ALLOC_ALIGN SZ_64K
#define EFI_ALLOC_LIMIT ((1UL << 48) - 1)
/*
* On ARM systems, virtually remapped UEFI runtime services are set up in two

2
drivers/firmware/efi/libstub/alignedmem.c
View File

@ -29,6 +29,8 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
efi_status_t status;
int slack;
max = min(max, EFI_ALLOC_LIMIT);
if (align < EFI_ALLOC_ALIGN)
align = EFI_ALLOC_ALIGN;

5
drivers/firmware/efi/libstub/arm64-stub.c
View File

@ -113,10 +113,11 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
if (status != EFI_SUCCESS) {
if (!check_image_region((u64)_text, kernel_memsize)) {
efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
} else if (IS_ALIGNED((u64)_text, min_kimg_align)) {
} else if (IS_ALIGNED((u64)_text, min_kimg_align) &&
(u64)_end < EFI_ALLOC_LIMIT) {
/*
* Just execute from wherever we were loaded by the
* UEFI PE/COFF loader if the alignment is suitable.
* UEFI PE/COFF loader if the placement is suitable.
*/
*image_addr = (u64)_text;
*reserve_size = 0;

4
drivers/firmware/efi/libstub/efistub.h
View File

@ -29,6 +29,10 @@
#define EFI_ALLOC_ALIGN EFI_PAGE_SIZE
#endif
#ifndef EFI_ALLOC_LIMIT
#define EFI_ALLOC_LIMIT ULONG_MAX
#endif
extern bool efi_nochunk;
extern bool efi_nokaslr;
extern int efi_loglevel;

2
drivers/firmware/efi/libstub/mem.c
View File

@ -89,6 +89,8 @@ efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
efi_physical_addr_t alloc_addr;
efi_status_t status;
max = min(max, EFI_ALLOC_LIMIT);
if (EFI_ALLOC_ALIGN > EFI_PAGE_SIZE)
return efi_allocate_pages_aligned(size, addr, max,
EFI_ALLOC_ALIGN,

2
drivers/firmware/efi/libstub/randomalloc.c
View File

@ -29,7 +29,7 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
return 0;
region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
(u64)ULONG_MAX);
(u64)EFI_ALLOC_LIMIT);
if (region_end < size)
return 0;