CVE-2021-47017 in Linux
Summary
by MITRE • 02/28/2024
In the Linux kernel, the following vulnerability has been resolved:
ath10k: Fix a use after free in ath10k_htc_send_bundle
In ath10k_htc_send_bundle, the bundle_skb could be freed by dev_kfree_skb_any(bundle_skb). But the bundle_skb is used later by bundle_skb->len.
As skb_len = bundle_skb->len, my patch replaces bundle_skb->len to skb_len after the bundle_skb was freed.
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2021-47017 represents a critical use-after-free condition within the ath10k wireless driver component of the Linux kernel. This flaw exists specifically in the ath10k_htc_send_bundle function which handles wireless packet transmission operations for Qualcomm Atheros wireless network adapters. The issue stems from improper memory management where a socket buffer (skb) pointer is freed but subsequently referenced, creating a scenario that could be exploited by malicious actors to execute arbitrary code or cause system instability.
The technical flaw manifests in the improper handling of the bundle_skb variable within the wireless driver's packet processing pipeline. When the ath10k_htc_send_bundle function processes wireless frames, it calls dev_kfree_skb_any() to release memory associated with the bundle_skb. However, the code continues to reference bundle_skb->len immediately after this free operation, creating a classic use-after-free vulnerability. This memory access pattern violates fundamental security principles and creates opportunities for attackers to manipulate memory contents or trigger denial-of-service conditions.
This vulnerability directly impacts the stability and security of Linux systems running affected wireless drivers, particularly those utilizing Qualcomm Atheros wireless hardware. The operational consequences extend beyond simple system crashes to potentially enable privilege escalation attacks and arbitrary code execution within the kernel context. Attackers could exploit this flaw by crafting malicious wireless packets that trigger the vulnerable code path, potentially leading to complete system compromise. The vulnerability affects systems with wireless networking capabilities using the ath10k driver, making it relevant across various computing environments from desktop systems to embedded devices.
The fix implemented addresses the core memory management issue by reordering operations to preserve the necessary length value before freeing the skb structure. This approach aligns with established security practices for preventing use-after-free vulnerabilities and follows the principle of avoiding references to freed memory. The patch ensures that bundle_skb->len is stored in a temporary variable (skb_len) before the memory deallocation occurs, thereby preventing the invalid memory access that could lead to system exploitation. This remediation technique corresponds to CWE-416, which specifically addresses use-after-free conditions in software development. The fix also demonstrates adherence to the ATT&CK framework's defense evasion techniques by preventing potential exploitation through memory corruption vulnerabilities.
The resolution of CVE-2021-47017 through this targeted patch represents a critical security update for Linux kernel users, particularly those operating wireless networking infrastructure. System administrators should prioritize applying this fix across affected deployments to maintain kernel security integrity and prevent potential exploitation by threat actors targeting wireless networking components. The vulnerability underscores the importance of thorough code review processes for kernel drivers and the critical need for proper memory management practices in security-sensitive code sections. This fix exemplifies the ongoing importance of vulnerability management in open-source kernel development and the collaborative efforts between security researchers and kernel maintainers to address critical security flaws.