Improper Input Validation Affecting kernel-rt-kvm package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-kvm package and not the kernel-rt-kvm package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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

mm/hwpoison: clear MF_COUNT_INCREASED before retrying get_any_page()

Hulk Robot reported a panic in put_page_testzero() when testing madvise() with MADV_SOFT_OFFLINE. The BUG() is triggered when retrying get_any_page(). This is because we keep MF_COUNT_INCREASED flag in second try but the refcnt is not increased.

page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:737!
invalid opcode: 0000 [#1] PREEMPT SMP
CPU: 5 PID: 2135 Comm: sshd Tainted: G    B             5.16.0-rc6-dirty #373
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: release_pages+0x53f/0x840
Call Trace:
  free_pages_and_swap_cache+0x64/0x80
  tlb_flush_mmu+0x6f/0x220
  unmap_page_range+0xe6c/0x12c0
  unmap_single_vma+0x90/0x170
  unmap_vmas+0xc4/0x180
  exit_mmap+0xde/0x3a0
  mmput+0xa3/0x250
  do_exit+0x564/0x1470
  do_group_exit+0x3b/0x100
  __do_sys_exit_group+0x13/0x20
  __x64_sys_exit_group+0x16/0x20
  do_syscall_64+0x34/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae
Modules linked in:
---[ end trace e99579b570fe0649 ]---
RIP: 0010:release_pages+0x53f/0x840

• https://access.redhat.com/security/cve/CVE-2021-47090
• https://git.kernel.org/stable/c/1f207076740101fed87074a6bc924dbe806f08a5
• https://git.kernel.org/stable/c/2a57d83c78f889bf3f54eede908d0643c40d5418
• https://git.kernel.org/stable/c/c691e7575eff76e563b0199c23ec46bd454f43e3