[PATCH 1/6] comedi: comedi_parport: validate the IRQ supplied by userspace

[Yogesh Gaur]

comedi boards are configured through the COMEDI_DEVCONFIG ioctl, so
it->options[1] is a number chosen by userspace. comedi_parport passes it to
request_irq() without checking it first, which lets an interrupt owned by
another irqdomain -- a PCI device's IO-APIC GSI, for instance -- be
claimed for this board. When the owner of that interrupt is later
released the descriptor is freed while this driver's handler is still
installed on it.

A parallel port asserts a legacy ISA interrupt, so the ISA range is the
right bound; it is also sufficient, because mp_chip_data->isa_irq is set
only by alloc_isa_irq_from_domain() and mp_unmap_irq() returns early when
it is set.

syzbot hit this one:

	remove_proc_entry: removing non-empty directory 'irq/20', leaking at least 'comedi_parport'
	WARNING: fs/proc/generic.c:747 at remove_proc_entry+0x4e7/0x610 fs/proc/generic.c:747
	Call Trace:
	 <TASK>
	 unregister_irq_proc+0x206/0x2a0 kernel/irq/proc.c:406
	 free_desc+0x89/0x330 kernel/irq/irqdesc.c:482
	 irq_free_descs+0x84/0xc0 kernel/irq/irqdesc.c:865
	 irq_domain_free_irqs+0x46a/0x5c0 kernel/irq/irqdomain.c:1917
	 mp_unmap_irq+0xf8/0x130 arch/x86/kernel/apic/io_apic.c:1061
	 acpi_unregister_gsi_ioapic+0x40/0x60 arch/x86/kernel/acpi/boot.c:722
	 acpi_pci_irq_disable+0x275/0x360 drivers/acpi/pci_irq.c:517
	 pci_disable_device+0x130/0x270 drivers/pci/pci.c:2206
	 pci_device_remove+0xb2/0x1d0 drivers/pci/pci-driver.c:512
	 device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
	 unbind_store+0xf8/0x110 drivers/base/bus.c:244
	 </TASK>

The leaked /proc entry the warning names is the mild part.
mp_chip_data->count tracks GSI mappings rather than request_irq() users,
and __setup_irq() takes no reference on the descriptor, so the irq_desc
is freed with the comedi irqaction still attached to it.

Bound the value before requesting it, as das16m1.c already does. An
out-of-range value is ignored rather than rejected, so the board still
attaches without interrupt support, exactly as it does today when
request_irq() fails.

Fixes: 241ab6ad7108 ("Staging: comedi: add comedi_parport driver")
Reported-by: syzbot+690d666eb12fca6e1e61@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=690d666eb12fca6e1e61
Assisted-by: LLM
Signed-off-by: Yogesh Gaur <yogeshgaur.83@xxxxxxxxx>
---
 drivers/comedi/drivers/comedi_parport.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/comedi_parport.c b/drivers/comedi/drivers/comedi_parport.c
index 57ee3f9dfba2..94284ff157ac 100644
--- a/drivers/comedi/drivers/comedi_parport.c
+++ b/drivers/comedi/drivers/comedi_parport.c
@@ -243,7 +243,8 @@ static int parport_attach(struct comedi_device *dev,
 	outb(0, dev->iobase + PARPORT_DATA_REG);
 	outb(0, dev->iobase + PARPORT_CTRL_REG);
 
-	if (it->options[1]) {
+	/* only ISA interrupts are valid on a parallel port */
+	if (it->options[1] >= 1 && it->options[1] <= 15) {
 		ret = request_irq(it->options[1], parport_interrupt, 0,
 				  dev->board_name, dev);
 		if (ret == 0)
-- 
2.55.0.windows.5