CVE-2026-46196

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

tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func()

When a tracepoint goes through the 0 -> 1 transition, tracepoint_add_func()

invokes the subsystem's ext->regfunc() before attempting to install the

new probe via func_add(). If func_add() then fails (for example, when

allocate_probes() cannot allocate a new probe array under memory pressure

and returns -ENOMEM), the function returns the error without calling the

matching ext->unregfunc(), leaving the side effects of regfunc() behind

with no installed probe to justify them.

For syscall tracepoints this is particularly unpleasant: syscall_regfunc()

bumps sys_tracepoint_refcount and sets SYSCALL_TRACEPOINT on every task.

After a leaked failure, the refcount is stuck at a non-zero value with no

consumer, and every task continues paying the syscall trace entry/exit

overhead until reboot. Other subsystems providing regfunc()/unregfunc()

pairs exhibit similarly scoped persistent state.

Mirror the existing 1 -> 0 cleanup and call ext->unregfunc() in the

func_add() error path, gated on the same condition used there so the

unwind is symmetric with the registration.