[PATCH] tty: hvc_iucv: fix off-by-one in number of supported devices

[Randy Dunlap]

MAX_HVC_IUCV_LINES == HVC_ALLOC_TTY_ADAPTERS == 8.
This is the number of entries in:
  static struct hvc_iucv_private *hvc_iucv_table[MAX_HVC_IUCV_LINES];

Sometimes hvc_iucv_table[] is limited by:
(a)	if (num > hvc_iucv_devices) // for error detection
or
(b)	for (i = 0; i < hvc_iucv_devices; i++) // in 2 places
(so these 2 don't agree; second one appears to be correct to me.)

hvc_iucv_devices can be 0..8. This is a counter.
(c)	if (hvc_iucv_devices > MAX_HVC_IUCV_LINES)

If hvc_iucv_devices == 8, (a) allows the code to access hvc_iucv_table[8].
Oops.

Fixes: 44a01d5ba8a4 ("[S390] s390/hvc_console: z/VM IUCV hypervisor console support")
Signed-off-by: Randy Dunlap <rdunlap at infradead.org>
---
No, I haven't seen an issue with this out in the wild.

Cc: Ahelenia Ziemiańska <nabijaczleweli at nabijaczleweli.xyz>
Cc: Hendrik Brueckner <brueckner at linux.vnet.ibm.com>
Cc: linuxppc-dev at lists.ozlabs.org
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Jiri Slaby <jirislaby at kernel.org>
Cc: linux-serial at vger.kernel.org
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: "Borislav Petkov (AMD)" <bp at alien8.de>

 drivers/tty/hvc/hvc_iucv.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20260128.orig/drivers/tty/hvc/hvc_iucv.c
+++ linux-next-20260128/drivers/tty/hvc/hvc_iucv.c
@@ -130,7 +130,7 @@ static struct iucv_handler hvc_iucv_hand
  */
 static struct hvc_iucv_private *hvc_iucv_get_private(uint32_t num)
 {
-	if (num > hvc_iucv_devices)
+	if (num >= hvc_iucv_devices)
 		return NULL;
 	return hvc_iucv_table[num];
 }