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authorRik van Riel <riel@surriel.com>2023-07-19 15:41:37 -0400
committerMike Rapoport (IBM) <rppt@kernel.org>2023-07-24 08:52:56 +0300
commit9e46e4dcd9d6cd88342b028dbfa5f4fb7483d39c (patch)
tree06bd454aba113d778aec8d8243a7a9b8526c49e2 /mm
parent6eaae198076080886b9e7d57f4ae06fa782f90ef (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')
-rw-r--r--mm/memblock.c4
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) {