CVE-2022-49778 [Medium] | Security Vulnerability in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud The page table check trigger BUG_ON() unexpectedly when collapse hugepage: ------------[ cut here ]------------ kernel BUG at mm/page_table_check.c:82! Internal error: Oops - BUG: 00000000f2000800 [#1] SMP Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750 Hardware name: linux,dummy-virt (DT) pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : page_table_check_clear.isra.0+0x258/0x3f0 lr : page_table_check_clear.isra.0+0x240/0x3f0 [...] Call trace: page_table_check_clear.isra.0+0x258/0x3f0 __page_table_check_pmd_clear+0xbc/0x108 pmdp_collapse_flush+0xb0/0x160 collapse_huge_page+0xa08/0x1080 hpage_collapse_scan_pmd+0xf30/0x1590 khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8 khugepaged+0x338/0x518 kthread+0x278/0x2f8 ret_from_fork+0x10/0x20 [...] Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it decrease file_map_count for a non-leaf pmd comes from collapse_huge_page(). and so trigger BUG_ON() unexpectedly. Fix this problem by using pmd_leaf() insteal of pmd_present() in pmd_user_accessible_page(). Moreover, use pud_leaf() for pud_user_accessible_page() too.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-05-02	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-05-02

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2022-49778

vendor	priority	summary	link
`debian`	unimportant	CVE-2022-49778 unimportant priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2022-49778
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2022-49778
`suse`	medium	CVE-2022-49778 severity moderate: SUSE including 69 source package names (cluster-md-kmp-default, dlm-kmp-default, …), 307 product×package rows across 52 product lines (SLES-LTSS-TERADATA 15 SP2, SUSE Liberty Linux 9, … (52 product lines)): Known Not Affected 264, Fixed 43.	https://www.suse.com/security/cve/CVE-2022-49778/
`ubuntu`	medium	CVE-2022-49778 medium priority: Ubuntu including 144 source packages (linux, linux-allwinner-5.19, …), 1285 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, trusty, upstream, xenial): DNE 921, ignored 146, not-affected 140, released 78.	https://ubuntu.com/security/CVE-2022-49778

Affected software / configurations for CVE-2022-49778

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 5.19, < 6.0.10	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.1	cpe:2.3:o:linux:linux_kernel:6.1:rc1::::::
linux	linux_kernel	6.1	cpe:2.3:o:linux:linux_kernel:6.1:rc2::::::
linux	linux_kernel	6.1	cpe:2.3:o:linux:linux_kernel:6.1:rc3::::::
linux	linux_kernel	6.1	cpe:2.3:o:linux:linux_kernel:6.1:rc4::::::
linux	linux_kernel	6.1	cpe:2.3:o:linux:linux_kernel:6.1:rc5::::::

References for CVE-2022-49778

URL	Tags
https://git.kernel.org/stable/c/2d458046df634088611d44fd77f45465e833ef78	Patch
https://git.kernel.org/stable/c/5b47348fc0b18a78c96f8474cc90b7525ad1bbfe	Patch

URL

CVE-2022-49778 | arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud

Exploit prediction scoring system (EPSS) score for CVE-2022-49778

Common vulnerability scoring system (CVSS) metrics for CVE-2022-49778

Weakness enumeration for CVE-2022-49778

OS Trackers for CVE-2022-49778

Affected software / configurations for CVE-2022-49778

References for CVE-2022-49778