CVE-2021-47200

drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap

Severity Score

5.5

*CVSS v3

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: drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap drm_gem_ttm_mmap() drops a reference to the gem object on success. If
the gem object's refcount == 1 on entry to drm_gem_prime_mmap(), that
drop will free the gem object, and the subsequent drm_gem_object_get()
will be a UAF. Fix by grabbing a reference before calling the mmap
helper. This issue was forseen when the reference dropping was adding in
commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"): "For that to work properly the drm_gem_object_get() call in drm_gem_ttm_mmap() must be moved so it happens before calling obj->funcs->mmap(), otherwise the gem refcount would go down to zero."

In the Linux kernel, the following vulnerability has been resolved: drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap drm_gem_ttm_mmap() drops a reference to the gem object on success. If the gem object's refcount == 1 on entry to drm_gem_prime_mmap(), that drop will free the gem object, and the subsequent drm_gem_object_get() will be a UAF. Fix by grabbing a reference before calling the mmap helper. This issue was forseen when the reference dropping was adding in commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"): "For that to work properly the drm_gem_object_get() call in drm_gem_ttm_mmap() must be moved so it happens before calling obj->funcs->mmap(), otherwise the gem refcount would go down to zero."

*Credits: N/A

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Attack Vector

Local

Attack Complexity

Low

Authentication

Single

Confidentiality

None

Integrity

None

Availability

Complete

* Common Vulnerability Scoring System

SSVC

Decision:Track*

Exploitation

None

Automatable

Tech. Impact

Total

* Organization's Worst-case Scenario

Timeline

2024-03-25 CVE Reserved
2024-04-10 CVE Published
2025-05-04 CVE Updated
2025-05-20 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (3)

URL	Tag	Source
https://git.kernel.org/stable/c/9786b65bc61acec63f923978c75e707afbb74bc7	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/4f8e469a2384dfa4047145b0093126462cbb6dc0	2021-11-25
https://git.kernel.org/stable/c/8244a3bc27b3efd057da154b8d7e414670d5044f	2021-11-03

URL	Date	SRC

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"				>= 5.5 < 5.15.5 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.5 < 5.15.5"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.5 < 5.16 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.5 < 5.16"		en		Affected