Subject: CVE-2024-35995: ACPI: CPPC: Use access_width over bit_width for system memory accesses

From: Greg Kroah-Hartman <[email-masked]>

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

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

ACPI: CPPC: Use access_width over bit_width for system memory accesses

To align with ACPI 6.3+, since bit_width can be any 8-bit value, it
cannot be depended on to be always on a clean 8b boundary. This was
uncovered on the Cobalt 100 platform.

SError Interrupt on CPU26, code 0xbe000011 -- SError
 CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted 5.15.2.1-13 #1
 Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION
 pstate: 62400009 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
 pc : cppc_get_perf_caps+0xec/0x410
 lr : cppc_get_perf_caps+0xe8/0x410
 sp : ffff8000155ab730
 x29: ffff8000155ab730 x28: ffff0080139d0038 x27: ffff0080139d0078
 x26: 0000000000000000 x25: ffff0080139d0058 x24: 00000000ffffffff
 x23: ffff0080139d0298 x22: ffff0080139d0278 x21: 0000000000000000
 x20: ffff00802b251910 x19: ffff0080139d0000 x18: ffffffffffffffff
 x17: 0000000000000000 x16: ffffdc7e111bad04 x15: ffff00802b251008
 x14: ffffffffffffffff x13: ffff013f1fd63300 x12: 0000000000000006
 x11: ffffdc7e128f4420 x10: 0000000000000000 x9 : ffffdc7e111badec
 x8 : ffff00802b251980 x7 : 0000000000000000 x6 : ffff0080139d0028
 x5 : 0000000000000000 x4 : ffff0080139d0018 x3 : 00000000ffffffff
 x2 : 0000000000000008 x1 : ffff8000155ab7a0 x0 : 0000000000000000
 Kernel panic - not syncing: Asynchronous SError Interrupt
 CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted
5.15.2.1-13 #1
 Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION
 Call trace:
  dump_backtrace+0x0/0x1e0
  show_stack+0x24/0x30
  dump_stack_lvl+0x8c/0xb8
  dump_stack+0x18/0x34
  panic+0x16c/0x384
  add_taint+0x0/0xc0
  arm64_serror_panic+0x7c/0x90
  arm64_is_fatal_ras_serror+0x34/0xa4
  do_serror+0x50/0x6c
  el1h_64_error_handler+0x40/0x74
  el1h_64_error+0x7c/0x80
  cppc_get_perf_caps+0xec/0x410
  cppc_cpufreq_cpu_init+0x74/0x400 [cppc_cpufreq]
  cpufreq_online+0x2dc/0xa30
  cpufreq_add_dev+0xc0/0xd4
  subsys_interface_register+0x134/0x14c
  cpufreq_register_driver+0x1b0/0x354
  cppc_cpufreq_init+0x1a8/0x1000 [cppc_cpufreq]
  do_one_initcall+0x50/0x250
  do_init_module+0x60/0x27c
  load_module+0x2300/0x2570
  __do_sys_finit_module+0xa8/0x114
  __arm64_sys_finit_module+0x2c/0x3c
  invoke_syscall+0x78/0x100
  el0_svc_common.constprop.0+0x180/0x1a0
  do_el0_svc+0x84/0xa0
  el0_svc+0x2c/0xc0
  el0t_64_sync_handler+0xa4/0x12c
  el0t_64_sync+0x1a4/0x1a8

Instead, use access_width to determine the size and use the offset and
width to shift and mask the bits to read/write out. Make sure to add a
check for system memory since pcc redefines the access_width to
subspace id.

If access_width is not set, then fall back to using bit_width.

[ rjw: Subject and changelog edits, comment adjustments ]

The Linux kernel CVE team has assigned CVE-2024-35995 to this issue.

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

	Fixed in 5.15.154 with commit 4949affd5288
	Fixed in 5.15.155 with commit b54c4632946a
	Fixed in 5.15.159 with commit 6dfd79ed04c5
	Fixed in 6.1.90 with commit 01fc53be672a
	Fixed in 6.6.30 with commit 1b890ae474d1
	Fixed in 6.8.9 with commit 6cb6b12b78dc
	Fixed in 6.9 with commit 2f4a4d63a193

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-2024-35995
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:
	drivers/acpi/cppc_acpi.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/4949affd5288b867cdf115f5b08d6166b2027f87
	https://git.kernel.org/stable/c/b54c4632946ae42f2b39ed38abd909bbf78cbcc2
	https://git.kernel.org/stable/c/6dfd79ed04c578f1d9a9a41ba5b2015cf9f03fc3
	https://git.kernel.org/stable/c/01fc53be672acae37e611c80cc0b4f3939584de3
	https://git.kernel.org/stable/c/1b890ae474d19800a6be1696df7fb4d9a41676e4
	https://git.kernel.org/stable/c/6cb6b12b78dcd8867a3fdbb1b6d0ed1df2b208d1
	https://git.kernel.org/stable/c/2f4a4d63a193be6fd530d180bb13c3592052904c