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A batch of fixes for the arm64 stub image loader:
 
 - fix a logic bug that can make the random page allocator fail
   spuriously
 - force reallocation of the Image when it overlaps with firmware
   reserved memory regions
 - fix an oversight that defeated on optimization introduced earlier
   where images loaded at a suitable offset are never moved if booting
   without randomization
 - complain about images that were not loaded at the right offset by the
   firmware image loader.
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Merge tag 'efi_urgent_for_v5.14_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull EFI fixes from Borislav Petkov:
 "A batch of fixes for the arm64 stub image loader:

   - fix a logic bug that can make the random page allocator fail
     spuriously

   - force reallocation of the Image when it overlaps with firmware
     reserved memory regions

   - fix an oversight that defeated on optimization introduced earlier
     where images loaded at a suitable offset are never moved if booting
     without randomization

   - complain about images that were not loaded at the right offset by
     the firmware image loader"

* tag 'efi_urgent_for_v5.14_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/libstub: arm64: Double check image alignment at entry
  efi/libstub: arm64: Warn when efi_random_alloc() fails
  efi/libstub: arm64: Relax 2M alignment again for relocatable kernels
  efi/libstub: arm64: Force Image reallocation if BSS was not reserved
  arm64: efi: kaslr: Fix occasional random alloc (and boot) failure
This commit is contained in:
Linus Torvalds 2021-08-15 06:38:26 -10:00
commit 12aef8acf0
2 changed files with 63 additions and 10 deletions
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71
drivers/firmware/efi/libstub/arm64-stub.c
View file

@ -35,15 +35,48 @@ efi_status_t check_platform_features(void)
}
/*
* Although relocatable kernels can fix up the misalignment with respect to
* MIN_KIMG_ALIGN, the resulting virtual text addresses are subtly out of
* sync with those recorded in the vmlinux when kaslr is disabled but the
* image required relocation anyway. Therefore retain 2M alignment unless
* KASLR is in use.
* Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
* to provide space, and fail to zero it). Check for this condition by double
* checking that the first and the last byte of the image are covered by the
* same EFI memory map entry.
*/
static u64 min_kimg_align(void)
static bool check_image_region(u64 base, u64 size)
{
return efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
unsigned long map_size, desc_size, buff_size;
efi_memory_desc_t *memory_map;
struct efi_boot_memmap map;
efi_status_t status;
bool ret = false;
int map_offset;
map.map = &memory_map;
map.map_size = &map_size;
map.desc_size = &desc_size;
map.desc_ver = NULL;
map.key_ptr = NULL;
map.buff_size = &buff_size;
status = efi_get_memory_map(&map);
if (status != EFI_SUCCESS)
return false;
for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
efi_memory_desc_t *md = (void *)memory_map + map_offset;
u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
/*
* Find the region that covers base, and return whether
* it covers base+size bytes.
*/
if (base >= md->phys_addr && base < end) {
ret = (base + size) <= end;
break;
}
}
efi_bs_call(free_pool, memory_map);
return ret;
}
efi_status_t handle_kernel_image(unsigned long *image_addr,
@ -56,6 +89,16 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
unsigned long kernel_size, kernel_memsize = 0;
u32 phys_seed = 0;
/*
* Although relocatable kernels can fix up the misalignment with
* respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
* subtly out of sync with those recorded in the vmlinux when kaslr is
* disabled but the image required relocation anyway. Therefore retain
* 2M alignment if KASLR was explicitly disabled, even if it was not
* going to be activated to begin with.
*/
u64 min_kimg_align = efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
if (!efi_nokaslr) {
status = efi_get_random_bytes(sizeof(phys_seed),
@ -76,6 +119,10 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
if (image->image_base != _text)
efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
if (!IS_ALIGNED((u64)_text, EFI_KIMG_ALIGN))
efi_err("FIRMWARE BUG: kernel image not aligned on %ldk boundary\n",
EFI_KIMG_ALIGN >> 10);
kernel_size = _edata - _text;
kernel_memsize = kernel_size + (_end - _edata);
*reserve_size = kernel_memsize;
@ -85,14 +132,18 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
* If KASLR is enabled, and we have some randomness available,
* locate the kernel at a randomized offset in physical memory.
*/
status = efi_random_alloc(*reserve_size, min_kimg_align(),
status = efi_random_alloc(*reserve_size, min_kimg_align,
reserve_addr, phys_seed);
if (status != EFI_SUCCESS)
efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
} else {
status = EFI_OUT_OF_RESOURCES;
}
if (status != EFI_SUCCESS) {
if (IS_ALIGNED((u64)_text, min_kimg_align())) {
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)) {
/*
* Just execute from wherever we were loaded by the
* UEFI PE/COFF loader if the alignment is suitable.
@ -103,7 +154,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
}
status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
ULONG_MAX, min_kimg_align());
ULONG_MAX, min_kimg_align);
if (status != EFI_SUCCESS) {
efi_err("Failed to relocate kernel\n");

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

@ -30,6 +30,8 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
(u64)ULONG_MAX);
if (region_end < size)
return 0;
first_slot = round_up(md->phys_addr, align);
last_slot = round_down(region_end - size + 1, align);