diff options
| author | Rik van Riel <riel@surriel.com> | 2023-07-19 15:41:37 -0400 |
|---|---|---|
| committer | Mike Rapoport (IBM) <rppt@kernel.org> | 2023-07-24 08:52:56 +0300 |
| commit | 9e46e4dcd9d6cd88342b028dbfa5f4fb7483d39c (patch) | |
| tree | 06bd454aba113d778aec8d8243a7a9b8526c49e2 /mm/memblock.c | |
| parent | 6eaae198076080886b9e7d57f4ae06fa782f90ef (diff) | |
mm,memblock: reset memblock.reserved to system init state to prevent UAF
The memblock_discard function frees the memblock.reserved.regions
array, which is good.
However, if a subsequent memblock_free (or memblock_phys_free) comes
in later, from for example ima_free_kexec_buffer, that will result in
a use after free bug in memblock_isolate_range.
When running a kernel with CONFIG_KASAN enabled, this will cause a
kernel panic very early in boot. Without CONFIG_KASAN, there is
a chance that memblock_isolate_range might scribble on memory
that is now in use by somebody else.
Avoid those issues by making sure that memblock_discard points
memblock.reserved.regions back at the static buffer.
If memblock_free is called after memblock memory is discarded, that will
print a warning in memblock_remove_region.
Signed-off-by: Rik van Riel <riel@surriel.com>
Link: https://lore.kernel.org/r/20230719154137.732d8525@imladris.surriel.com
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Diffstat (limited to 'mm/memblock.c')
| -rw-r--r-- | mm/memblock.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/memblock.c b/mm/memblock.c index f9e61e565a53..c39b36378f5d 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -374,6 +374,10 @@ void __init memblock_discard(void) kfree(memblock.reserved.regions); else memblock_free_late(addr, size); + /* Reset to prevent UAF from stray frees. */ + memblock.reserved.regions = memblock_reserved_init_regions; + memblock.reserved.cnt = 1; + memblock_remove_region(&memblock.reserved, 0); } if (memblock.memory.regions != memblock_memory_init_regions) { |