CVE-2022-48770 in Linux
Summary
by MITRE • 06/20/2024
In the Linux kernel, the following vulnerability has been resolved:
bpf: Guard against accessing NULL pt_regs in bpf_get_task_stack()
task_pt_regs() can return NULL on powerpc for kernel threads. This is then used in __bpf_get_stack() to check for user mode, resulting in a kernel oops. Guard against this by checking return value of task_pt_regs() before trying to obtain the call chain.
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Analysis
by VulDB Data Team • 01/07/2025
The vulnerability identified as CVE-2022-48770 represents a critical kernel-level issue within the Linux kernel's eBPF (extended Berkeley Packet Filter) subsystem that affects systems running on powerpc architecture. This flaw manifests in the bpf_get_task_stack() function where improper handling of null pointer references leads to kernel oops conditions and potential system instability. The vulnerability specifically impacts kernel threads where the task_pt_regs() function returns NULL, creating a dangerous scenario that can be exploited to cause system crashes or potentially enable privilege escalation attacks.
The technical root cause of this vulnerability lies in the improper validation of return values from the task_pt_regs() function within the __bpf_get_stack() implementation. When kernel threads execute on powerpc systems, the task_pt_regs() function may legitimately return NULL pointers, particularly for threads that do not have associated user-space execution contexts. However, the bpf_get_task_stack() function fails to validate this return value before proceeding with operations that assume a valid pt_regs structure exists. This null pointer dereference occurs during stack trace collection operations, where the kernel attempts to determine whether execution is occurring in user mode or kernel mode, leading to immediate system crashes.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise system integrity and availability. Attackers with access to execute eBPF programs could exploit this weakness to trigger kernel oops conditions that may result in denial of service attacks against target systems. The vulnerability affects systems running Linux kernel versions prior to the fix, particularly those utilizing powerpc architecture where kernel threads frequently interact with the bpf subsystem. This creates a significant risk for enterprise environments where powerpc-based systems may be running critical infrastructure applications that rely on eBPF for network monitoring, security enforcement, or system diagnostics.
This vulnerability aligns with CWE-476, which identifies NULL pointer dereference as a fundamental security weakness in software development practices. The issue demonstrates poor defensive programming techniques where developers failed to implement proper null pointer validation before dereferencing function return values. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain targeting kernel-level persistence or privilege escalation opportunities, though the immediate impact remains focused on system stability and availability rather than direct privilege elevation. The fix implemented in the kernel addresses this by adding proper validation checks to ensure that task_pt_regs() return values are verified before proceeding with stack trace operations, thereby preventing the null pointer dereference that leads to kernel oops conditions. Organizations should prioritize applying the relevant kernel updates to mitigate this vulnerability and ensure continued system stability across their powerpc-based infrastructure deployments.