linux-cve-announce - CVE-2025-37960: memblock: Accept allocated memory before use in memblock_double

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Message-ID: <2025052004-CVE-2025-37960-97de@gregkh>
Date: Tue, 20 May 2025 18:02:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37960: memblock: Accept allocated memory before use in memblock_double_array()

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2025-37960 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.5 with commit dcdfdd40fa82b6704d2841938e5c8ec3051eb0d6 and fixed in 6.12.29 with commit d66a22f6a432a9dd376c9b365d7dc89bd416909c
	Issue introduced in 6.5 with commit dcdfdd40fa82b6704d2841938e5c8ec3051eb0d6 and fixed in 6.14.7 with commit aa513e69e011a2b19fa22ce62ce35effbd5e0c81
	Issue introduced in 6.5 with commit dcdfdd40fa82b6704d2841938e5c8ec3051eb0d6 and fixed in 6.15-rc6 with commit da8bf5daa5e55a6af2b285ecda460d6454712ff4

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-37960
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	mm/memblock.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/d66a22f6a432a9dd376c9b365d7dc89bd416909c
	https://git.kernel.org/stable/c/aa513e69e011a2b19fa22ce62ce35effbd5e0c81
	https://git.kernel.org/stable/c/da8bf5daa5e55a6af2b285ecda460d6454712ff4