CVE-2017-9984 in Linux
Summary
by MITRE
The snd_msnd_interrupt function in sound/isa/msnd/msnd_pinnacle.c in the Linux kernel through 4.11.7 allows local users to cause a denial of service (over-boundary access) or possibly have unspecified other impact by changing the value of a message queue head pointer between two kernel reads of that value, aka a "double fetch" vulnerability.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability identified as CVE-2017-9984 resides within the Linux kernel's sound subsystem, specifically in the snd_msnd_interrupt function located in sound/isa/msnd/msnd_pinnacle.c. This flaw represents a classic double fetch vulnerability that exploits a race condition in kernel memory management. The vulnerability affects Linux kernel versions through 4.11.7 and demonstrates a critical weakness in how the kernel handles message queue operations within the MSND (Microsoft Sound) driver architecture. The issue manifests when a local user can manipulate the value of a message queue head pointer between two consecutive kernel reads of that same pointer value, creating a window where the kernel's memory access patterns become unpredictable and potentially dangerous.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the kernel's interrupt handling routine for the MSND driver. When the snd_msnd_interrupt function processes incoming messages, it performs two separate reads of the same message queue head pointer without adequate locking or validation between these operations. This double fetch creates a scenario where an attacker can modify the pointer value during the brief window between the first and second reads, leading to memory access violations. The consequence of this vulnerability includes potential kernel crashes due to over-boundary access, which results in denial of service conditions, but could also potentially allow for more severe impacts including privilege escalation or arbitrary code execution depending on the specific exploitation context.
From an operational standpoint, this vulnerability presents significant risks to systems running affected Linux kernel versions, particularly those utilizing the MSND sound driver for audio processing. The local privilege escalation aspect means that any user with access to the system can potentially trigger this vulnerability, making it a serious concern for multi-user environments or systems where untrusted users might have shell access. The impact extends beyond simple service disruption as the memory corruption could potentially be leveraged to execute malicious code within kernel space, thereby compromising the entire system security posture. This vulnerability aligns with CWE-367 weakness classification, which specifically addresses time-of-check to time-of-use race conditions, and represents a clear violation of the principle of least privilege in kernel space operations.
The mitigation strategies for CVE-2017-9984 primarily involve upgrading to a patched kernel version where the double fetch vulnerability has been addressed through proper synchronization mechanisms and pointer validation. System administrators should prioritize patching affected systems immediately, as the vulnerability is exploitable by local users and provides a pathway to system compromise. Additional protective measures include implementing proper kernel hardening techniques such as stack canaries, address space layout randomization, and disabling unnecessary audio drivers to reduce attack surface. The remediation process should also involve monitoring for exploitation attempts through kernel log analysis and implementing intrusion detection systems that can identify suspicious memory access patterns. Organizations should consider adopting the ATT&CK framework's T1068 technique for privilege escalation to better understand and defend against potential exploitation paths stemming from this vulnerability. The fix implemented in patched versions typically involves adding proper locking mechanisms around the pointer access operations to prevent the race condition that enables the double fetch attack vector.