memblock fixes for v6.5-rc4

Hi Linus,

The following changes since commit 6eaae198076080886b9e7d57f4ae06fa782f90ef:

Linux 6.5-rc3 (2023-07-23 15:24:10 -0700)

are available in the Git repository at:

https://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock.git tags/fixes-2023-07-27

for you to fetch changes up to 9e46e4dcd9d6cd88342b028dbfa5f4fb7483d39c:

mm,memblock: reset memblock.reserved to system init state to prevent UAF (2023-07-24 08:52:56 +0300)

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memblock: reset memblock.reserved to system init state to prevent UAF

A call to memblock_free() or memblock_phys_free() issued after memblock data is discarded will result in use after free in memblock_isolate_range().

When CONFIG_KASAN is enabled, this will cause a panic 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() or memblock_phys_free() is called after memblock memory is discarded, that will print a warning in memblock_remove_region().

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Rik van Riel (1):
mm,memblock: reset memblock.reserved to system init state to prevent UAF

 mm/memblock.c | 4 ++++
 1 file changed, 4 insertions(+)

Sincerely yours,
Mike.

The merge message shouldn't just be a repeat of the commit message.

I ended up cutting it down a bit, but would prefer to just get a concise summary rather than the repeat of the message for the fix.

Linus