memblock: Accept allocated memory before use in memblock_double_array()

In the Linux kernel, the following vulnerability has been resolved:

memblock: Accept allocated memory before use in memblock_double_array()

When increasing the array size in memblock_double_array() and the slab

is not yet available, a call to memblock_find_in_range() is used to

reserve/allocate memory. However, the range returned may not have been

accepted, which can result in a crash when booting an SNP guest:

RIP: 0010:memcpy_orig+0x68/0x130

Code: ...

RSP: 0000:ffffffff9cc03ce8 EFLAGS: 00010006

RAX: ff11001ff83e5000 RBX: 0000000000000000 RCX: fffffffffffff000

RDX: 0000000000000bc0 RSI: ffffffff9dba8860 RDI: ff11001ff83e5c00

RBP: 0000000000002000 R08: 0000000000000000 R09: 0000000000002000

R10: 000000207fffe000 R11: 0000040000000000 R12: ffffffff9d06ef78

R13: ff11001ff83e5000 R14: ffffffff9dba7c60 R15: 0000000000000c00

memblock_double_array+0xff/0x310

memblock_add_range+0x1fb/0x2f0

memblock_reserve+0x4f/0xa0

memblock_alloc_range_nid+0xac/0x130

memblock_alloc_internal+0x53/0xc0

memblock_alloc_try_nid+0x3d/0xa0

swiotlb_init_remap+0x149/0x2f0

mem_init+0xb/0xb0

mm_core_init+0x8f/0x350

start_kernel+0x17e/0x5d0

x86_64_start_reservations+0x14/0x30

x86_64_start_kernel+0x92/0xa0

secondary_startup_64_no_verify+0x194/0x19b

Mitigate this by calling accept_memory() on the memory range returned

before the slab is available.

Prior to v6.12, the accept_memory() interface used a 'start' and 'end'

parameter instead of 'start' and 'size', therefore the accept_memory()

call must be adjusted to specify 'start + size' for 'end' when applying

to kernels prior to v6.12.