In the Linux kernel, the following vulnerability has been resolved:
comedi: comedi_parport: deal with premature interrupt
Syzbot reported a general protection fault in
comedi_get_is_subdevice_running(), which was called from the interrupt
handler parport_interrupt() in the comedi_parport driver, but it
does not currently have a C reproducer for the problem. Its
probably due to a premature interrupt for one of two reasons:
- The driver sets up the interrupt handler before the comedi subdevices used by the interrupt handler have been allocated, but does not disable the interrupt in the parallel ports CTRL register first.
- The driver uses a user-supplied I/O port base address which Syzbot would have supplied, but it might not be backed by real parallel port hardware.
Change the initialization order in the drivers comedi attach handler
(parport_attach()) so that the hardware registers are initialized
before the interrupt handler is requested. This should prevent
premature interrupts occurring for real hardware.
Also add a test to the interrupt handler to ensure the comedi device is fully attached and return early if it isnt.
References
- https://git.kernel.org/stable/c/086a9ae3c5df63ec11033a8c0b3f6a1fd295ddd1
- https://git.kernel.org/stable/c/17221216ae8ce6a24e8a4e787382e3ebc81b88a8
- https://git.kernel.org/stable/c/5d059ce0e6a2f6f8b97273499d47b8f917097b48
- https://git.kernel.org/stable/c/b061bb4dca49fd93063359d3805387235818778c
- https://git.kernel.org/stable/c/cf26dd2d841583c54a87005c4934b92fddb930c3