Re: [PATCH] memblock: Accept allocated memory before use in memblock_double_array()

[Mike Rapoport]

From: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>

On Thu, 08 May 2025 12:24:10 -0500, Tom Lendacky wrote:
> 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
> 
> [...]

Applied to fixes branch of memblock.git tree, thanks!

[1/1] memblock: Accept allocated memory before use in memblock_double_array()
      commit: da8bf5daa5e55a6af2b285ecda460d6454712ff4

tree: https://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock
branch: fixes

--
Sincerely yours,
Mike.