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relocator: Protect grub_relocator_alloc_chunk_align() max_addr against integer underflow

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This commit introduces integer underflow mitigation in max_addr calculation
in grub_relocator_alloc_chunk_align() invocation.

It consists of 2 fixes:
  1. Introduced grub_relocator_alloc_chunk_align_safe() wrapper function to perform
     sanity check for min/max and size values, and to make safe invocation of
     grub_relocator_alloc_chunk_align() with validated max_addr value. Replace all
     invocations such as grub_relocator_alloc_chunk_align(..., min_addr, max_addr - size, size, ...)
     by grub_relocator_alloc_chunk_align_safe(..., min_addr, max_addr, size, ...).
  2. Introduced UP_TO_TOP32(s) macro for the cases where max_addr is 32-bit top
     address (0xffffffff - size + 1) or similar.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Alexey Makhalov 2020-07-08 01:44:38 +00:00 • committed by Daniel Kiper
parent caea56d1f8
commit 61ff5602fe
13 changed files with 69 additions and 58 deletions
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29
include/grub/relocator.h
View file

@ -49,6 +49,35 @@ grub_relocator_alloc_chunk_align (struct grub_relocator *rel,
int preference,
int avoid_efi_boot_services);
/*
* Wrapper for grub_relocator_alloc_chunk_align() with purpose of
* protecting against integer underflow.
*
* Compare to its callee, max_addr has different meaning here.
* It covers entire chunk and not just start address of the chunk.
*/
static inline grub_err_t
grub_relocator_alloc_chunk_align_safe (struct grub_relocator *rel,
grub_relocator_chunk_t *out,
grub_phys_addr_t min_addr,
grub_phys_addr_t max_addr,
grub_size_t size, grub_size_t align,
int preference,
int avoid_efi_boot_services)
{
/* Sanity check and ensure following equation (max_addr - size) is safe. */
if (max_addr < size || (max_addr - size) < min_addr)
return GRUB_ERR_OUT_OF_RANGE;
return grub_relocator_alloc_chunk_align (rel, out, min_addr,
max_addr - size,
size, align, preference,
avoid_efi_boot_services);
}
/* Top 32-bit address minus s bytes and plus 1 byte. */
#define UP_TO_TOP32(s) ((~(s) & 0xffffffff) + 1)
#define GRUB_RELOCATOR_PREFERENCE_NONE 0
#define GRUB_RELOCATOR_PREFERENCE_LOW 1
#define GRUB_RELOCATOR_PREFERENCE_HIGH 2