# CVE-2022-48897: linux: In the Linux kernel, the following vulnerability has been resolved:  arm64/mm: fix incorrect file_map_count for inval...

CVE-2022-48897 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-48897, released August 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-48897
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 21, 2024

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.7-1 | [DEBIAN-CVE-2022-48897](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48897.md) | Aug 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.1.7-1 | [DEBIAN-CVE-2022-48897](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48897.md) | Aug 21, 2024 |
| Linux | linux Debian 14 | 6.1.7-1 | [DEBIAN-CVE-2022-48897](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48897.md) | Aug 21, 2024 |

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