Bug 1226620 (CVE-2022-48731)

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

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

mm/kmemleak: avoid scanning potential huge holes

When using devm_request_free_mem_region() and devm_memremap_pages() to
add ZONE_DEVICE memory, if requested free mem region's end pfn were
huge(e.g., 0x400000000), the node_end_pfn() will be also huge (see
move_pfn_range_to_zone()).  Thus it creates a huge hole between
node_start_pfn() and node_end_pfn().

We found on some AMD APUs, amdkfd requested such a free mem region and
created a huge hole.  In such a case, following code snippet was just
doing busy test_bit() looping on the huge hole.

  for (pfn = start_pfn; pfn < end_pfn; pfn++) {
	struct page *page = pfn_to_online_page(pfn);
		if (!page)
			continue;
	...
  }

So we got a soft lockup:

  watchdog: BUG: soft lockup - CPU#6 stuck for 26s! [bash:1221]
  CPU: 6 PID: 1221 Comm: bash Not tainted 5.15.0-custom #1
  RIP: 0010:pfn_to_online_page+0x5/0xd0
  Call Trace:
    ? kmemleak_scan+0x16a/0x440
    kmemleak_write+0x306/0x3a0
    ? common_file_perm+0x72/0x170
    full_proxy_write+0x5c/0x90
    vfs_write+0xb9/0x260
    ksys_write+0x67/0xe0
    __x64_sys_write+0x1a/0x20
    do_syscall_64+0x3b/0xc0
    entry_SYSCALL_64_after_hwframe+0x44/0xae

I did some tests with the patch.

(1) amdgpu module unloaded

before the patch:

  real    0m0.976s
  user    0m0.000s
  sys     0m0.968s

after the patch:

  real    0m0.981s
  user    0m0.000s
  sys     0m0.973s

(2) amdgpu module loaded

before the patch:

  real    0m35.365s
  user    0m0.000s
  sys     0m35.354s

after the patch:

  real    0m1.049s
  user    0m0.000s
  sys     0m1.042s

The Linux kernel CVE team has assigned CVE-2022-48731 to this issue.


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

	Fixed in 5.4.178 with commit d3533ee20e9a
	Fixed in 5.10.99 with commit 352715593e81
	Fixed in 5.15.22 with commit a5389c80992f
	Fixed in 5.16.8 with commit cebb0aceb21a
	Fixed in 5.17 with commit c10a0f877fe0

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-2022-48731
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/kmemleak.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/d3533ee20e9a0e2e8f60384da7450d43d1c63d1a
	https://git.kernel.org/stable/c/352715593e81b917ce1b321e794549815b850134
	https://git.kernel.org/stable/c/a5389c80992f0001ee505838fe6a8b20897ce96e
	https://git.kernel.org/stable/c/cebb0aceb21ad91429617a40e3a17444fabf1529
	https://git.kernel.org/stable/c/c10a0f877fe007021d70f9cada240f42adc2b5db

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2022-48731
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2022/CVE-2022-48731.mbox
https://git.kernel.org/stable/c/d3533ee20e9a0e2e8f60384da7450d43d1c63d1a
https://git.kernel.org/stable/c/352715593e81b917ce1b321e794549815b850134
https://git.kernel.org/stable/c/a5389c80992f0001ee505838fe6a8b20897ce96e
https://git.kernel.org/stable/c/cebb0aceb21ad91429617a40e3a17444fabf1529
https://git.kernel.org/stable/c/c10a0f877fe007021d70f9cada240f42adc2b5db