CVE-2021-47383

tty: Fix out-of-bound vmalloc access in imageblit

Severity Score

6.6

*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:

tty: Fix out-of-bound vmalloc access in imageblit

This issue happens when a userspace program does an ioctl
FBIOPUT_VSCREENINFO passing the fb_var_screeninfo struct
containing only the fields xres, yres, and bits_per_pixel
with values.

If this struct is the same as the previous ioctl, the
vc_resize() detects it and doesn't call the resize_screen(),
leaving the fb_var_screeninfo incomplete. And this leads to
the updatescrollmode() calculates a wrong value to
fbcon_display->vrows, which makes the real_y() return a
wrong value of y, and that value, eventually, causes
the imageblit to access an out-of-bound address value.

To solve this issue I made the resize_screen() be called
even if the screen does not need any resizing, so it will
"fix and fill" the fb_var_screeninfo independently.

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: tty: corrige el acceso vmalloc fuera de los límites en imageblit. Este problema ocurre cuando un programa de espacio de usuario realiza un ioctl FBIOPUT_VSCREENINFO pasando la estructura fb_var_screeninfo que contiene solo los campos xres, yres y bits_per_pixel con valores. Si esta estructura es la misma que la ioctl anterior, vc_resize() la detecta y no llama a resize_screen(), dejando fb_var_screeninfo incompleto. Y esto lleva a que updatecrollmode() calcule un valor incorrecto para fbcon_display->vrows, lo que hace que real_y() devuelva un valor incorrecto de y, y ese valor, eventualmente, hace que imageblit acceda a un valor de dirección fuera de los límites. . Para resolver este problema, hice que se llamara a resize_screen() incluso si la pantalla no necesita ningún cambio de tamaño, por lo que "arreglará y completará" fb_var_screeninfo de forma independiente.

*Credits: N/A

CVSS Scores

Red Hatv3.1 6.6

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-05-21 CVE Reserved
2024-05-21 CVE Published
2024-05-22 EPSS Updated
2024-08-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-125: Out-of-bounds Read

CAPEC

References (10)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/7e71fcedfda6f7de18f850a6b36e78d78b04476f	2021-10-06
https://git.kernel.org/stable/c/70aed03b1d5a5df974f456cdc8eedb213c94bb8b	2021-10-06
https://git.kernel.org/stable/c/067c694d06040db6f0c65281bb358452ca6d85b9	2021-10-06
https://git.kernel.org/stable/c/8a6a240f52e14356386030d8958ae8b1761d2325	2021-10-06
https://git.kernel.org/stable/c/883f7897a25e3ce14a7f274ca4c73f49ac84002a	2021-10-06
https://git.kernel.org/stable/c/d570c48dd37dbe8fc6875d4461d01a9554ae2560	2021-10-06
https://git.kernel.org/stable/c/699d926585daa6ec44be556cdc1ab89e5d54557b	2021-10-07
https://git.kernel.org/stable/c/3b0c406124719b625b1aba431659f5cdc24a982c	2021-07-21

URL	Date	SRC
https://access.redhat.com/security/cve/CVE-2021-47383	2024-08-14
https://bugzilla.redhat.com/show_bug.cgi?id=2282357	2024-08-14

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"				< 4.4.286 Search vendor "Linux" for product "Linux Kernel" and version " < 4.4.286"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 4.9.285 Search vendor "Linux" for product "Linux Kernel" and version " < 4.9.285"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 4.14.249 Search vendor "Linux" for product "Linux Kernel" and version " < 4.14.249"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 4.19.209 Search vendor "Linux" for product "Linux Kernel" and version " < 4.19.209"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.4.151 Search vendor "Linux" for product "Linux Kernel" and version " < 5.4.151"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.10.71 Search vendor "Linux" for product "Linux Kernel" and version " < 5.10.71"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.14.10 Search vendor "Linux" for product "Linux Kernel" and version " < 5.14.10"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.15 Search vendor "Linux" for product "Linux Kernel" and version " < 5.15"		en		Affected