CVE-2022-49799 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing: Fix wild-memory-access in register_synth_event()
In register_synth_event(), if set_synth_event_print_fmt() failed, then both trace_remove_event_call() and unregister_trace_event() will be called, which means the trace_event_call will call __unregister_trace_event() twice. As the result, the second unregister will causes the wild-memory-access.
register_synth_event set_synth_event_print_fmt failed trace_remove_event_call event_remove if call->event.funcs then __unregister_trace_event (first call) unregister_trace_event __unregister_trace_event (second call)
Fix the bug by avoiding to call the second __unregister_trace_event() by checking if the first one is called.
general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN PTI
KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]
CPU: 0 PID: 3807 Comm: modprobe Not tainted 6.1.0-rc1-00186-g76f33a7eedb4 #299 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014 RIP: 0010:unregister_trace_event+0x6e/0x280 Code: 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02 00 0f 85 0e 02 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 63 08 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 e2 01 00 00 49 89 2c 24 48 85 ed 74 28 e8 7a 9b RSP: 0018:ffff88810413f370 EFLAGS: 00010a06 RAX: dffffc0000000000 RBX: ffff888105d050b0 RCX: 0000000000000000 RDX: 1bd5a00000000024 RSI: ffff888119e276e0 RDI: ffffffff835a8b20 RBP: dead000000000100 R08: 0000000000000000 R09: fffffbfff0913481 R10: ffffffff8489a407 R11: fffffbfff0913480 R12: dead000000000122 R13: ffff888105d050b8 R14: 0000000000000000 R15: ffff888105d05028 FS: 00007f7823e8d540(0000) GS:ffff888119e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7823e7ebec CR3: 000000010a058002 CR4: 0000000000330ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __create_synth_event+0x1e37/0x1eb0 create_or_delete_synth_event+0x110/0x250 synth_event_run_command+0x2f/0x110 test_gen_synth_cmd+0x170/0x2eb [synth_event_gen_test]
synth_event_gen_test_init+0x76/0x9bc [synth_event_gen_test]
do_one_initcall+0xdb/0x480 do_init_module+0x1cf/0x680 load_module+0x6a50/0x70a0 __do_sys_finit_module+0x12f/0x1c0 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd
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Analysis
by VulDB Data Team • 11/07/2025
The vulnerability described in CVE-2022-49799 represents a critical double-free condition within the Linux kernel's tracing subsystem, specifically in the register_synth_event() function. This flaw arises from improper handling of error paths during synthetic event registration, leading to wild memory access patterns that can result in system crashes or potential privilege escalation. The issue manifests when set_synth_event_print_fmt() fails during event creation, triggering a cascade of cleanup operations that inadvertently call __unregister_trace_event() twice on the same trace_event_call structure.
The technical implementation of this vulnerability stems from the kernel's tracing infrastructure where synthetic events are dynamically created to monitor system behavior. When the print format setup fails, the code path executes both trace_remove_event_call() and unregister_trace_event() functions sequentially. The first function call invokes __unregister_trace_event() through event_remove(), while the second function directly calls __unregister_trace_event() again, creating a scenario where the same memory region gets deallocated twice. This double-unregister operation causes memory corruption that manifests as general protection faults and KASAN (Kernel Address Sanitizer) warnings indicating wild-memory-access in the range 0xdead000000000120-0xdead000000000127, suggesting memory access violations to non-canonical addresses.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential security risk within the kernel's memory management subsystem. The double-free condition can lead to arbitrary code execution if an attacker can manipulate the memory layout or trigger the specific error path. This vulnerability directly maps to CWE-415: Double Free, which is classified as a high-severity issue in the Common Weakness Enumeration catalog. The ATT&CK framework categorizes this under T1068: Exploitation for Privilege Escalation, as kernel-level memory corruption can be leveraged to gain elevated privileges. The specific code paths involved demonstrate poor resource management where the kernel fails to properly track the state of trace_event_call structures during error conditions.
The fix for this vulnerability involves implementing proper state checking to prevent the second __unregister_trace_event() call from executing when the first one has already been invoked. This requires modifying the register_synth_event() function to maintain a flag or state variable that tracks whether the cleanup operation has already occurred. Such a solution aligns with secure coding practices recommended in the Linux kernel security guidelines, specifically addressing the need for proper resource management in error paths. The mitigation strategy must ensure that event cleanup operations are idempotent or properly guarded against multiple execution, preventing the memory corruption that results from the double-free condition. This fix ultimately prevents the kernel from attempting to free already-released memory structures, thereby eliminating the potential for system crashes and security exploits that could arise from the wild memory access patterns described in the vulnerability report.