CVE-2021-47079 in Linux
Summary
by MITRE • 03/02/2024
In the Linux kernel, the following vulnerability has been resolved:
platform/x86: ideapad-laptop: fix a NULL pointer dereference
The third parameter of dytc_cql_command should not be NULL since it will be dereferenced immediately.
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2021-47079 represents a critical NULL pointer dereference flaw within the Linux kernel's platform x86 subsystem, specifically affecting the ideapad-laptop driver component. This issue arises from improper parameter validation within the dytc_cql_command function implementation, where the third parameter is not adequately checked for NULL values before subsequent dereferencing operations. The vulnerability exists in the kernel's handling of certain hardware-specific commands for ideapad laptop devices, making it particularly relevant to users of Lenovo ideapad series laptops that utilize this driver interface.
The technical nature of this vulnerability falls under the category of improper input validation and memory management errors, which aligns with CWE-476, specifically the weakness of NULL pointer dereference. When the dytc_cql_command function is invoked with a NULL value as its third parameter, the kernel code immediately attempts to dereference this pointer without prior validation, leading to an immediate system crash or potential privilege escalation depending on the execution context. This flaw represents a classic case of insufficient bounds checking and parameter validation that can be exploited by malicious actors to cause system instability or gain unauthorized access to kernel memory spaces.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be leveraged to cause denial of service conditions that affect the entire system functionality. Attackers with local access or those able to trigger the specific hardware command sequence could potentially exploit this vulnerability to crash the kernel, forcing system reboots or rendering the device unusable. The vulnerability is particularly concerning because it affects the platform x86 subsystem which is fundamental to system operation, and the ideapad-laptop driver is commonly used across various laptop models, making the attack surface quite broad. Additionally, this flaw can potentially be combined with other kernel vulnerabilities to achieve more severe outcomes such as privilege escalation or information disclosure.
Mitigation strategies for CVE-2021-47079 should focus on immediate kernel updates and patches provided by the Linux kernel maintainers, which address the NULL pointer dereference by implementing proper parameter validation before dereferencing operations. System administrators should prioritize applying the relevant security patches as soon as they become available through their distribution channels. Additional protective measures include implementing proper kernel hardening techniques such as stack canaries, kernel address space layout randomization, and strict module loading controls. Monitoring for unusual system behavior or kernel panic messages can help detect exploitation attempts, while maintaining current security patches and kernel versions ensures protection against similar vulnerabilities. The fix typically involves adding a simple NULL check before the dereference operation, following established secure coding practices that align with the ATT&CK framework's defense evasion and privilege escalation tactics. Organizations should also consider implementing kernel module blacklisting for vulnerable drivers until proper patches are applied, and conduct thorough security assessments of their kernel configurations to identify other potential similar vulnerabilities.