CVE-2026-46196tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/5787052e5f69beb649f3d6a80a8aa37d9e683e4e
• https://git.kernel.org/stable/c/4f1756d043e56ea2e9a6c858fb290a0cf6fc2251
• https://git.kernel.org/stable/c/36ff362235307af95152d510b53c2d9b8773a342
• https://git.kernel.org/stable/c/247ed8a969f981bfba3112fd4bb441eaa6cef59c
• https://git.kernel.org/stable/c/7bcadb3c2bc1cf60690e931aadd35fb7bd646a49
• https://git.kernel.org/stable/c/2c5b8eeea006eb694c81631cd5713d494b80be90
• https://git.kernel.org/stable/c/342829e042ac00f3d68d442ea92873fb6683f494
• https://git.kernel.org/stable/c/fad217e16fded7f3c09f8637b0f6a224d58b5f2e
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html