[PATCH] comedi: addi_apci_3xxx: fix subdevice count underallocation

[Yang Zi]

In apci3xxx_auto_attach(), the number of subdevices is computed with

    n_subdevices = (board->ai_n_chan ? 0 : 1) + board->has_ao + ...

The ternary is inverted: when the board has analog input channels
(ai_n_chan != 0), it counts 0 instead of 1, so the AI subdevice that is
actually created is not accounted for. As a result
comedi_alloc_subdevices() allocates one entry too few, and the later
subdevice initialization (notably the TTL Digital I/O subdevice, which
is populated last) writes past the end of the allocated array, causing a
slab out-of-bounds write.

Flip the ternary to count 1 when ai_n_chan is non-zero and 0 otherwise,
matching the subdevice creation order in the function.

Signed-off-by: Yang Zi <2959243019@xxxxxx>
---
diff --git a/drivers/comedi/drivers/addi_apci_3xxx.c b/drivers/comedi/drivers/addi_apci_3xxx.c
index 695cce103177..1dcda82d9503 100644
--- a/drivers/comedi/drivers/addi_apci_3xxx.c
+++ b/drivers/comedi/drivers/addi_apci_3xxx.c
@@ -787,7 +787,7 @@ static int apci3xxx_auto_attach(struct comedi_device *dev,
             dev->irq = pcidev->irq;
     }
 
-    n_subdevices = (board->ai_n_chan ? 0 : 1) + board->has_ao +
+    n_subdevices = (board->ai_n_chan ? 1 : 0) + board->has_ao +
                board->has_dig_in + board->has_dig_out +
                board->has_ttl_io;
     ret = comedi_alloc_subdevices(dev, n_subdevices);