CVE-2022-49800 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing: Fix memory leak in test_gen_synth_cmd() and test_empty_synth_event()
test_gen_synth_cmd() only free buf in fail path, hence buf will leak when there is no failure. Add kfree(buf) to prevent the memleak. The same reason and solution in test_empty_synth_event().
unreferenced object 0xffff8881127de000 (size 2048): comm "modprobe", pid 247, jiffies 4294972316 (age 78.756s) hex dump (first 32 bytes): 20 67 65 6e 5f 73 79 6e 74 68 5f 74 65 73 74 20 gen_synth_test 20 70 69 64 5f 74 20 6e 65 78 74 5f 70 69 64 5f pid_t next_pid_ backtrace: [<000000004254801a>] kmalloc_trace+0x26/0x100
[<0000000039eb1cf5>] 0xffffffffa00083cd
[<000000000e8c3bc8>] 0xffffffffa00086ba
[<00000000c293d1ea>] do_one_initcall+0xdb/0x480
[<00000000aa189e6d>] do_init_module+0x1cf/0x680
[<00000000d513222b>] load_module+0x6a50/0x70a0
[<000000001fd4d529>] __do_sys_finit_module+0x12f/0x1c0
[<00000000b36c4c0f>] do_syscall_64+0x3f/0x90
[<00000000bbf20cf3>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
unreferenced object 0xffff8881127df000 (size 2048): comm "modprobe", pid 247, jiffies 4294972324 (age 78.728s) hex dump (first 32 bytes): 20 65 6d 70 74 79 5f 73 79 6e 74 68 5f 74 65 73 empty_synth_tes 74 20 20 70 69 64 5f 74 20 6e 65 78 74 5f 70 69 t pid_t next_pi backtrace: [<000000004254801a>] kmalloc_trace+0x26/0x100
[<00000000d4db9a3d>] 0xffffffffa0008071
[<00000000c31354a5>] 0xffffffffa00086ce
[<00000000c293d1ea>] do_one_initcall+0xdb/0x480
[<00000000aa189e6d>] do_init_module+0x1cf/0x680
[<00000000d513222b>] load_module+0x6a50/0x70a0
[<000000001fd4d529>] __do_sys_finit_module+0x12f/0x1c0
[<00000000b36c4c0f>] do_syscall_64+0x3f/0x90
[<00000000bbf20cf3>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/07/2025
The vulnerability identified as CVE-2022-49800 resides within the Linux kernel's tracing subsystem, specifically affecting the test functions test_gen_synth_cmd() and test_empty_synth_event(). This issue represents a classic memory leak scenario where allocated memory is not properly deallocated under normal execution paths. The flaw manifests when these test functions allocate memory buffers using kmalloc but only release them in error or failure conditions. The absence of proper deallocation in successful execution paths leads to gradual memory consumption that can eventually impact system stability and performance. This type of vulnerability falls under the category of memory management errors commonly tracked by CWE-401 as "Improper Release of Memory Before Removing Last Reference" and aligns with ATT&CK technique T1070.004 for "File and Registry Permission Changes" since improper memory handling can lead to resource exhaustion attacks. The memory leak occurs during kernel module initialization, as evidenced by the stack traces showing execution paths through do_one_initcall, do_init_module, and load_module functions, indicating that the issue affects kernel module loading processes. The leaked memory objects, each sized at 2048 bytes, are clearly identifiable through kernel debugging tools with their respective identifiers gen_synth_test and empty_synth_test, demonstrating that the memory allocation occurs in the context of kernel tracing functionality. The vulnerability directly impacts system resource management and can contribute to memory fragmentation over time, particularly in systems that frequently load and unload kernel modules or execute tracing operations.
The technical root cause stems from incomplete error handling logic within the kernel's tracing test framework. When test_gen_synth_cmd() and test_empty_synth_event() execute successfully without encountering errors, they fail to call kfree() on the allocated buffer memory, creating persistent memory leaks. This pattern indicates a fundamental flaw in resource management where allocated resources are not consistently released regardless of execution outcome. The kernel's memory allocation tracing system, kmalloc_trace, provides detailed stack traces that help identify the precise locations where memory was allocated, showing that both functions allocate memory during module initialization phases. The leaked memory remains unreferenced and uncollectable by the kernel's memory management subsystem, creating a persistent resource drain that can accumulate over time. The specific backtrace paths through kernel initialization functions demonstrate that this vulnerability impacts the core module loading infrastructure rather than being limited to user-space applications. This memory leak pattern represents a common anti-pattern in kernel development where proper resource cleanup is only implemented in error paths but not in normal execution paths. The vulnerability affects systems running affected kernel versions where the tracing subsystem is enabled and actively used during module loading operations, particularly impacting embedded systems or servers that frequently load kernel modules.
The operational impact of CVE-2022-49800 extends beyond simple memory consumption to potentially compromise system stability and availability. While the leak itself may appear minor at individual instances, repeated module loading operations can accumulate significant memory consumption that eventually leads to memory pressure conditions. This can result in system slowdowns, memory allocation failures, or even system crashes in extreme cases where memory becomes critically low. The vulnerability is particularly concerning in long-running systems or those with high module loading frequency, as the memory leak compounds over time and can lead to resource exhaustion attacks. Systems using kernel tracing features extensively may experience degraded performance as available memory decreases, potentially affecting real-time processing capabilities or other critical kernel operations. The memory leak also contributes to memory fragmentation, which can further degrade system performance and make it harder for the kernel to allocate large contiguous memory blocks. Organizations relying on kernel tracing for debugging or monitoring purposes face increased risk of operational disruptions due to this memory management issue. The vulnerability can be exploited by malicious actors who intentionally load and unload kernel modules repeatedly to accelerate memory exhaustion, making it a potential vector for denial-of-service attacks.
Mitigation strategies for CVE-2022-49800 should focus on immediate kernel updates and code-level fixes. The most effective solution involves applying the kernel patch that ensures proper memory deallocation in both test functions by adding kfree(buf) calls in all execution paths, not just error conditions. System administrators should prioritize updating to kernel versions that include the fix, particularly those that have addressed the memory leak in the tracing subsystem. Monitoring systems should be enhanced to detect unusual memory consumption patterns that may indicate memory leaks, especially during kernel module loading operations. While the vulnerability is limited to test functions within the tracing subsystem, organizations should conduct thorough testing of kernel module loading processes to ensure no other similar memory management issues exist. The fix should be applied across all systems that utilize kernel tracing features, particularly in production environments where memory stability is critical. Regular system audits should include checks for memory leaks in kernel modules and tracing subsystems to prevent similar issues from emerging. Additionally, implementing automated memory monitoring tools can help detect and alert on memory consumption anomalies that may indicate the presence of similar vulnerabilities in other kernel components. The solution aligns with security best practices for kernel development and follows established protocols for memory management in kernel space as defined by Linux kernel security standards and security frameworks.