CVE-2022-49891 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing: kprobe: Fix memory leak in test_gen_kprobe/kretprobe_cmd()
test_gen_kprobe_cmd() only free buf in fail path, hence buf will leak when there is no failure. Move kfree(buf) from fail path to common path to prevent the memleak. The same reason and solution in test_gen_kretprobe_cmd().
unreferenced object 0xffff888143b14000 (size 2048): comm "insmod", pid 52490, jiffies 4301890980 (age 40.553s) hex dump (first 32 bytes): 70 3a 6b 70 72 6f 62 65 73 2f 67 65 6e 5f 6b 70 p:kprobes/gen_kp 72 6f 62 65 5f 74 65 73 74 20 64 6f 5f 73 79 73 robe_test do_sys backtrace: [] kmalloc_trace+0x27/0xa0
[] 0xffffffffa059006f
[] do_one_initcall+0x87/0x2a0
[] do_init_module+0xdf/0x320
[] load_module+0x3006/0x3390
[] __do_sys_finit_module+0x113/0x1b0
[] do_syscall_64+0x35/0x80
[] entry_SYSCALL_64_after_hwframe+0x46/0xb0
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Analysis
by VulDB Data Team • 05/01/2025
The vulnerability identified as CVE-2022-49891 represents a memory leak within the Linux kernel's tracing subsystem, specifically affecting kprobe and kretprobe functionality. This issue resides in the kernel's test infrastructure rather than core operational code, making it particularly concerning for development and testing environments where kernel modules are frequently loaded and unloaded. The flaw manifests in the test_gen_kprobe_cmd() and test_gen_kretprobe_cmd() functions, which are part of the kernel's tracing test suite designed to validate kprobe operations. The memory leak occurs due to improper resource management during module initialization, where allocated memory buffers are not consistently freed across all execution paths.
The technical root cause stems from conditional memory management logic that only frees allocated buffers in error or failure paths, while neglecting to release memory in successful execution scenarios. This pattern creates a classic memory leak vulnerability where kernel memory becomes unreferenced but remains allocated, leading to gradual memory consumption over time. The specific memory allocation occurs through kmalloc_trace() function as evidenced by the backtrace, with the leaked object showing a 2048-byte buffer allocated in the context of the kprobes test module. The leaked memory segment demonstrates characteristics consistent with kernel heap allocation patterns, where the buffer was allocated during module initialization and subsequently leaked when the module's initialization completed successfully without triggering the error handling path.
From an operational perspective, this vulnerability poses significant risks to systems running kernel tracing tests, particularly in development environments where modules are frequently loaded and unloaded during testing cycles. While the leak is contained within test infrastructure rather than production kernel code, it represents a potential vector for resource exhaustion attacks if exploited in environments where kernel modules are regularly loaded. The vulnerability affects the kernel's memory management efficiency and could contribute to system performance degradation over extended periods of testing activity. The memory leak also aligns with CWE-401, which classifies memory leaks as a common weakness in software systems, specifically categorized under improper cleanup of resources.
The solution implemented addresses this issue by moving the kfree() call from the error handling path to a common execution path, ensuring that allocated buffers are consistently freed regardless of execution outcome. This fix follows established best practices for resource management and aligns with the principle of deterministic cleanup in kernel code. The remediation approach prevents the memory leak by ensuring that all allocated resources are properly released, maintaining kernel memory integrity. This type of vulnerability would typically be categorized under the ATT&CK technique T1059.006 for kernel modules and could potentially be leveraged in advanced persistent threat scenarios where attackers might attempt to exhaust system resources through repeated module loading operations. The fix demonstrates proper defensive programming practices that should be applied to all kernel subsystems handling dynamic memory allocation to prevent similar vulnerabilities from manifesting in production code paths.