CVE-2021-47492

mm, thp: bail out early in collapse_file for writeback page

Severity Score

5.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

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

mm, thp: bail out early in collapse_file for writeback page

Currently collapse_file does not explicitly check PG_writeback, instead,
page_has_private and try_to_release_page are used to filter writeback
pages. This does not work for xfs with blocksize equal to or larger
than pagesize, because in such case xfs has no page->private.

This makes collapse_file bail out early for writeback page. Otherwise,
xfs end_page_writeback will panic as follows.

page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32
aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:"libtest.so"
flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback)
raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8
raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000
page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u))
page->mem_cgroup:ffff0000c3e9a000
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:1212!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in:
BUG: Bad page state in process khugepaged pfn:84ef32
xfs(E)
page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32
libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ...
CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ...
pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)
Call trace:
end_page_writeback+0x1c0/0x214
iomap_finish_page_writeback+0x13c/0x204
iomap_finish_ioend+0xe8/0x19c
iomap_writepage_end_bio+0x38/0x50
bio_endio+0x168/0x1ec
blk_update_request+0x278/0x3f0
blk_mq_end_request+0x34/0x15c
virtblk_request_done+0x38/0x74 [virtio_blk]
blk_done_softirq+0xc4/0x110
__do_softirq+0x128/0x38c
__irq_exit_rcu+0x118/0x150
irq_exit+0x1c/0x30
__handle_domain_irq+0x8c/0xf0
gic_handle_irq+0x84/0x108
el1_irq+0xcc/0x180
arch_cpu_idle+0x18/0x40
default_idle_call+0x4c/0x1a0
cpuidle_idle_call+0x168/0x1e0
do_idle+0xb4/0x104
cpu_startup_entry+0x30/0x9c
secondary_start_kernel+0x104/0x180
Code: d4210000 b0006161 910c8021 94013f4d (d4210000)
---[ end trace 4a88c6a074082f8c ]---
Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: mm, thp: rescatar temprano en el colapso_archivo para la página de reescritura. Actualmente, colapso_archivo no verifica explícitamente PG_writeback; en su lugar, page_has_private y try_to_release_page se utilizan para filtrar las páginas de reescritura. Esto no funciona para xfs con un tamaño de bloque igual o mayor que el tamaño de página, porque en tal caso xfs no tiene página->privada. Esto hace que colapso_file salga anticipadamente de la página de reescritura. De lo contrario, xfs end_page_writeback entrará en pánico de la siguiente manera. página:fffffe00201bcc80 refcount:0 mapcount:0 mapeo:ffff0003f88c86a8 índice:0x0 pfn:0x84ef32 aops:xfs_address_space_operaciones [xfs] ino:30000b7 nombre dentry:"libtest.so" banderas: 0x57fffe0000008027(bloqueado|referenciado| actualización|activo|reescritura) sin formato : 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8 crudo: 0000000000000000 00000000000000000 00000000ffffffff página volcada porque: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u)) page->mem_cgroup:ffff0000c3e9a000 ----------- -[ cortar aquí ]------------ ¡ERROR del kernel en include/linux/mm.h:1212! Error interno: Ups - ERROR: 0 [#1] Módulos SMP vinculados en: ERROR: Estado de página incorrecto en el proceso khugepaged pfn:84ef32 xfs(E) page:fffffe00201bcc80 refcount:0 mapcount:0 mapeo:0 index:0x0 pfn:0x84ef32 libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ... CPU: 25 PID: 0 Comm: swapper/25 Kdump: cargado Contaminado: ... pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) Seguimiento de llamadas: end_page_writeback+0x1c0/0x214 iomap_finish_page_writeback+0x13c/0x204 iomap_finish_ioend+0xe8/0x19c iomap_writepage_end_bio+0x38/0x50 bio_endio+0x168/0x1ec blk_update_request+0x278/0x 3f0 blk_mq_end_request+0x34/0x15c virtblk_request_done+0x38/0x74 [virtio_blk ] blk_done_softirq+0xc4/0x110 __do_softirq+0x128/0x38c __irq_exit_rcu+0x118/0x150 irq_exit+0x1c/0x30 __handle_domain_irq+0x8c/0xf0 gic_handle_irq+0x84/0x108 xcc/0x180 arch_cpu_idle+0x18/0x40 default_idle_call+0x4c/0x1a0 cpuidle_idle_call+0x168/ 0x1e0 do_idle+0xb4/0x104 cpu_startup_entry+0x30/0x9c second_start_kernel+0x104/0x180 Código: d4210000 b0006161 910c8021 94013f4d (d4210000) ---[ end trace 4a88c6a074082f 8c ]--- Pánico en el kernel - no se sincroniza: Ups - ERROR: excepción fatal en la interrupción

*Credits: N/A

CVSS Scores

Red Hatv3.1 5.5

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-05-22 CVE Reserved
2024-05-22 CVE Published
2024-05-23 EPSS Updated
2024-12-19 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-372: Incomplete Internal State Distinction

CAPEC

References (6)

URL	Tag	Source
https://git.kernel.org/stable/c/99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/69a7fa5cb0de06c8956b040f19a7248c8c8308ca	2021-11-02
https://git.kernel.org/stable/c/5e669d8ab30ab61dec3c36e27b4711f07611e6fc	2021-11-02
https://git.kernel.org/stable/c/74c42e1baacf206338b1dd6b6199ac964512b5bb	2021-10-29

URL	Date	SRC
https://access.redhat.com/security/cve/CVE-2021-47492	2024-09-18
https://bugzilla.redhat.com/show_bug.cgi?id=2282924	2024-09-18

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.10.77 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.10.77"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.14.16 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.14.16"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.15 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.15"		en		Affected