CVE-2022-48897 arm64/mm: fix incorrect file_map_count for invalid pmd
A bug in the Linux kernel arm64 memory management causes a kernel panic when splitting hugepages, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-48897?
CVE-2022-48897 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Aug 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
arm64/mm: fix incorrect file_map_count for invalid pmd
The page table check trigger BUG_ON() unexpectedly when split hugepage:
------------[ cut here ]------------ kernel BUG at mm/page_table_check.c:119! Internal error: Oops - BUG: 00000000f2000800 [#1] SMP Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 7 PID: 210 Comm: transhuge-stres Not tainted 6.1.0-rc3+ #748 Hardware name: linux,dummy-virt (DT) pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : page_table_check_set.isra.0+0x398/0x468 lr : page_table_check_set.isra.0+0x1c0/0x468 [...] Call trace: page_table_check_set.isra.0+0x398/0x468 __page_table_check_pte_set+0x160/0x1c0 __split_huge_pmd_locked+0x900/0x1648 __split_huge_pmd+0x28c/0x3b8 unmap_page_range+0x428/0x858 unmap_single_vma+0xf4/0x1c8 zap_page_range+0x2b0/0x410 madvise_vma_behavior+0xc44/0xe78 do_madvise+0x280/0x698 __arm64_sys_madvise+0x90/0xe8 invoke_syscall.constprop.0+0xdc/0x1d8 do_el0_svc+0xf4/0x3f8 el0_svc+0x58/0x120 el0t_64_sync_handler+0xb8/0xc0 el0t_64_sync+0x19c/0x1a0 [...]
On arm64, pmd_leaf() will return true even if the pmd is invalid due to pmd_present_invalid() check. So in pmdp_invalidate() the file_map_count will not only decrease once but also increase once. Then in set_pte_at(), the file_map_count increase again, and so trigger BUG_ON() unexpectedly.
Add !pmd_present_invalid() check in pmd_user_accessible_page() to fix the problem.
Which versions are affected by CVE-2022-48897?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-48897?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-48897 being exploited?
There is no known exploitation of CVE-2022-48897 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-48897, GHSA-j4gx-6m2g-9p7c, UBUNTU-CVE-2022-48897.