CVE-2022-48897: linux kernel — Fix

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.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.19 — 6.1.7
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/21e5eca0ac9046da9918a919bc92b7b5a78d27e7 https://git.kernel.org/stable/c/74c2f81054510d45b813548cb0a1c4ebf87cdd5f

Frequently Asked Questions

What is CVE-2022-48897? +

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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2022-48897? +

CVE-2022-48897 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2022-48897? +

CVE-2022-48897 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2022-48897? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2022-48897