#VU88214 Improper locking in Linux kernel - CVE-2021-46921

Vulnerability identifier: #VU88214

Vulnerability risk: Low

CVSSv4.0: 4.3 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-46921

CWE-ID: CWE-667

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to perform a denial of service attack.

The vulnerability exists due to improper locking within the queued_write_lock_slowpath() function in kernel/locking/qrwlock.c. A local user can crash the kernel.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Linux kernel: 4.19, 4.19.1, 4.19.2, 4.19.3, 4.19.4, 4.19.5, 4.19.6, 4.19.7, 4.19.8, 4.19.9, 4.19.10, 4.19.11, 4.19.12, 4.19.13, 4.19.14, 4.19.15, 4.19.16, 4.19.17, 4.19.18, 4.19.19, 4.19.20, 4.19.21, 4.19.22, 4.19.23, 4.19.24, 4.19.25, 4.19.26, 4.19.27, 4.19.28, 4.19.29, 4.19.30, 4.19.31, 4.19.32, 4.19.33, 4.19.34, 4.19.35, 4.19.36, 4.19.37, 4.19.38, 4.19.39, 4.19.40, 4.19.41, 4.19.42, 4.19.43, 4.19.44, 4.19.45, 4.19.46, 4.19.47, 4.19.48, 4.19.49, 4.19.50, 4.19.51, 4.19.52, 4.19.53, 4.19.54, 4.19.55, 4.19.56, 4.19.57, 4.19.58, 4.19.59, 4.19.60, 4.19.61, 4.19.62, 4.19.63, 4.19.64, 4.19.65, 4.19.66, 4.19.67, 4.19.68, 4.19.69, 4.19.70, 4.19.71, 4.19.72, 4.19.73, 4.19.74, 4.19.75, 4.19.76, 4.19.77, 4.19.78, 4.19.79, 4.19.80, 4.19.81, 4.19.82, 4.19.83, 4.19.84, 4.19.85, 4.19.86, 4.19.87, 4.19.88, 4.19.89, 4.19.90, 4.19.91, 4.19.92, 4.19.93, 4.19.94, 4.19.95, 4.19.96, 4.19.97, 4.19.98, 4.19.99, 4.19.100, 4.19.101, 4.19.102, 4.19.103, 4.19.104, 4.19.105, 4.19.106, 4.19.107, 4.19.108, 4.19.109, 4.19.110, 4.19.111, 4.19.112, 4.19.113, 4.19.114, 4.19.115, 4.19.116, 4.19.117, 4.19.118, 4.19.118-2, 4.19.119, 4.19.120, 4.19.121, 4.19.122, 4.19.123, 4.19.124, 4.19.125, 4.19.126, 4.19.127, 4.19.128, 4.19.129, 4.19.130, 4.19.131, 4.19.132, 4.19.133, 4.19.134, 4.19.135, 4.19.136, 4.19.137, 4.19.138, 4.19.139, 4.19.140, 4.19.141, 4.19.142, 4.19.143, 4.19.144, 4.19.145, 4.19.146, 4.19.147, 4.19.148, 4.19.149, 4.19.150, 4.19.151, 4.19.152, 4.19.153, 4.19.154, 4.19.155, 4.19.156, 4.19.157, 4.19.158, 4.19.159, 4.19.160, 4.19.161, 4.19.162, 4.19.163, 4.19.164, 4.19.165, 4.19.166, 4.19.167, 4.19.168, 4.19.169, 4.19.170, 4.19.171, 4.19.172, 4.19.173, 4.19.174, 4.19.175, 4.19.176, 4.19.177, 4.19.178, 4.19.179, 4.19.180, 4.19.181, 4.19.182, 4.19.183, 4.19.184, 4.19.185, 4.19.186, 4.19.187, 4.19.188, 5.4, 5.4.0, 5.4.0 rc6, 5.4.1, 5.4.2, 5.4.3, 5.4.4, 5.4.5, 5.4.6, 5.4.7, 5.4.8, 5.4.9, 5.4.10, 5.4.11, 5.4.12, 5.4.13, 5.4.14, 5.4.15, 5.4.16, 5.4.17, 5.4.18, 5.4.19, 5.4.20, 5.4.21, 5.4.22, 5.4.23, 5.4.24, 5.4.25, 5.4.26, 5.4.27, 5.4.28, 5.4.29, 5.4.30, 5.4.31, 5.4.32, 5.4.33, 5.4.34, 5.4.35, 5.4.36, 5.4.37, 5.4.38, 5.4.39, 5.4.40, 5.4.41, 5.4.42, 5.4.43, 5.4.44, 5.4.45, 5.4.46, 5.4.47, 5.4.48, 5.4.49, 5.4.50, 5.4.51, 5.4.52, 5.4.53, 5.4.54, 5.4.55, 5.4.56, 5.4.57, 5.4.58, 5.4.59, 5.4.60, 5.4.61, 5.4.62, 5.4.63, 5.4.64, 5.4.65, 5.4.66, 5.4.67, 5.4.68, 5.4.69, 5.4.70, 5.4.71, 5.4.72, 5.4.73, 5.4.74, 5.4.75, 5.4.76, 5.4.77, 5.4.78, 5.4.79, 5.4.80, 5.4.81, 5.4.82, 5.4.83, 5.4.84, 5.4.85, 5.4.86, 5.4.87, 5.4.88, 5.4.89, 5.4.90, 5.4.91, 5.4.92, 5.4.93, 5.4.94, 5.4.95, 5.4.96, 5.4.97, 5.4.98, 5.4.99, 5.4.100, 5.4.101, 5.4.102, 5.4.103, 5.4.104, 5.4.105, 5.4.106, 5.4.107, 5.4.108, 5.4.109, 5.4.110, 5.4.111, 5.4.112, 5.4.113, 5.4.114, 5.10, 5.10 rc1, 5.10 rc2, 5.10 rc3, 5.10 rc4, 5.10 rc5, 5.10 rc7, 5.10.1, 5.10.2, 5.10.3, 5.10.4, 5.10.5, 5.10.6, 5.10.7, 5.10.8, 5.10.9, 5.10.10, 5.10.11, 5.10.12, 5.10.13, 5.10.14, 5.10.15, 5.10.16, 5.10.17, 5.10.18, 5.10.19, 5.10.20, 5.10.21, 5.10.22, 5.10.23, 5.10.24, 5.10.25, 5.10.26, 5.10.27, 5.10.28, 5.10.29, 5.10.30, 5.10.31, 5.10.32, 5.11, 5.11 rc1, 5.11.1, 5.11.2, 5.11.3, 5.11.4, 5.11.5, 5.11.6, 5.11.7, 5.11.8, 5.11.9, 5.11.10, 5.11.11, 5.11.12, 5.11.13, 5.11.14, 5.11.15, 5.11.16, 5.12 rc1, 5.12 rc2, 5.12 rc3, 5.12 rc4, 5.12 rc6, 5.12 rc8

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External links
https://git.kernel.org/stable/c/5902f9453a313be8fe78cbd7e7ca9dba9319fc6e
https://git.kernel.org/stable/c/82808cc026811fbc3ecf0c0b267a12a339eead56
https://git.kernel.org/stable/c/82fa9ced35d88581cffa4a1c856fc41fca96d80a
https://git.kernel.org/stable/c/d558fcdb17139728347bccc60a16af3e639649d2
https://git.kernel.org/stable/c/84a24bf8c52e66b7ac89ada5e3cfbe72d65c1896
https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.189
https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.10.33
https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.17
https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12
https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.4.115

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.