CVE-2026-99247: tracing: Do not initialize tracefs work if tracing is disabled

In the Linux kernel, the following vulnerability has been resolved:

tracing: Do not initialize tracefs work if tracing is disabled

If trace buffer allocation fails during early boot (e.g. in earlytraceinit() -> allocatetracebuffers()), tracingdisabled is left set to 1 and the global trace array events list remains uninitialized.

Later during boot, tracerinittracefs() (invoked via fsinitcall) queues tracerfsinitwork asynchronously without checking if tracing was disabled. When tracerinittracefsworkfunc() runs, it calls eventtraceinit() and inittracertracefs(&globaltrace, NULL) unconditionally. This leads to findeventfile() dereferencing an uninitialized tr->events list, causing an early boot NULL pointer dereference Oops:

BUG: Kernel NULL pointer dereference on read at 0x00000010 Faulting instruction address: 0xc000000000485be0 Oops: Kernel access of bad area, sig: 7 [#1] ... NIP [c000000000485be0] findeventfile+0x70/0x3c0 LR [c000000000448874] inittracertracefs+0x274/0xc80 Call Trace: inittracertracefs+0x274/0xc80 tracerinittracefsworkfunc+0x50/0x320 processonework+0x1e8/0x5c0 workerthread+0x1dc/0x3d0 kthread+0x194/0x1b0 startkernelthread+0x14/0x18

Check tracingdisabled at the beginning of tracerinittracefsworkfunc() and return immediately if tracing is disabled or failed to initialize, preventing the crash.