CVE-2017-8244 in Android
Summary
by MITRE
In core_info_read and inst_info_read in all Android releases from CAF using the Linux kernel, variable "dbg_buf", "dbg_buf->curr" and "dbg_buf->filled_size" could be modified by different threads at the same time, but they are not protected with mutex or locks. Buffer overflow is possible on race conditions. "buffer->curr" itself could also be overwritten, which means that it may point to anywhere of kernel memory (for write).
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Analysis
by VulDB Data Team • 12/23/2020
This vulnerability exists in the Linux kernel implementations used by Android devices, specifically affecting core_info_read and inst_info_read functions across all Android releases from Code Aurora Forum. The flaw stems from improper synchronization mechanisms within the kernel code where the dbg_buf structure and its associated members including dbg_buf->curr and dbg_buf->filled_size are accessed concurrently by multiple threads without adequate mutex or lock protection. The race condition occurs when different threads attempt to modify these shared variables simultaneously, creating potential for unpredictable behavior and memory corruption. When multiple threads access the same memory locations without proper synchronization, the order of operations becomes non-deterministic and can lead to data inconsistency.
The technical impact of this vulnerability is significant as it creates conditions where buffer overflow can occur during race conditions, potentially allowing attackers to overwrite memory locations with arbitrary data. The most concerning aspect is that buffer->curr itself can be overwritten, which means an attacker could manipulate this pointer to point to arbitrary locations within kernel memory. This creates a potential path for privilege escalation and arbitrary code execution within the kernel space, as the attacker could redirect execution flow or corrupt critical kernel structures. The vulnerability directly relates to CWE-362, which describes race conditions that occur when multiple threads access shared resources without proper synchronization mechanisms. This weakness is particularly dangerous because it operates at the kernel level where the attacker could gain elevated privileges and potentially compromise the entire system.
The operational impact extends beyond simple buffer overflows to encompass potential system instability and complete compromise of device security. When an attacker can manipulate the buffer->curr pointer to point to kernel memory locations, they gain the ability to perform write operations at arbitrary kernel addresses, which could lead to privilege escalation attacks. This vulnerability is particularly concerning for mobile devices as it affects the core kernel functionality that handles information reading operations, potentially allowing malicious actors to access sensitive kernel data or manipulate critical system components. The attack surface is broad as this affects all Android releases from Code Aurora Forum, meaning that a large number of devices could be vulnerable simultaneously. The vulnerability can be exploited through kernel-level attacks that leverage the race condition to gain unauthorized access to kernel memory regions, making it a critical security concern for mobile device manufacturers and users.
Mitigation strategies should focus on implementing proper synchronization mechanisms to protect shared variables within the kernel code. The most effective approach involves adding mutex locks or other synchronization primitives around the critical sections where dbg_buf and its members are accessed by multiple threads. This ensures that only one thread can modify these shared resources at any given time, eliminating the race condition that leads to buffer overflow. Additionally, input validation should be strengthened to prevent buffer overflows even when race conditions occur, including bounds checking for buffer operations and proper initialization of memory structures. System administrators and device manufacturers should prioritize updating kernel implementations to include proper locking mechanisms and ensure that all threads accessing shared resources are properly synchronized. The solution aligns with ATT&CK technique T1068 which involves exploiting local privilege escalation vulnerabilities, and requires defensive measures that include kernel hardening, proper memory management, and robust synchronization protocols to prevent unauthorized access to kernel memory regions.