ISDN: Fix data access out of array bounds

Fix against access random data bytes outside the dev->chanmap array.
Thanks to Oliver Neukum for pointing me to this issue.

Signed-off-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/isdn/i4l/isdn_common.c b/drivers/isdn/i4l/isdn_common.c
index ec5f4046412f..4910bca52640 100644
--- a/drivers/isdn/i4l/isdn_common.c
+++ b/drivers/isdn/i4l/isdn_common.c
@@ -1135,7 +1135,7 @@ isdn_read(struct file *file, char __user *buf, size_t count, loff_t * off)
                         if (count > dev->drv[drvidx]->stavail)
                                 count = dev->drv[drvidx]->stavail;
                         len = dev->drv[drvidx]->interface->readstat(buf, count,
-                                                drvidx, isdn_minor2chan(minor));
+                                drvidx, isdn_minor2chan(minor - ISDN_MINOR_CTRL));
                         if (len < 0) {
                                 retval = len;
                                 goto out;
@@ -1207,7 +1207,8 @@ isdn_write(struct file *file, const char __user *buf, size_t count, loff_t * off
                  */
                 if (dev->drv[drvidx]->interface->writecmd)
                         retval = dev->drv[drvidx]->interface->
-                                writecmd(buf, count, drvidx, isdn_minor2chan(minor));
+                                writecmd(buf, count, drvidx,
+                                isdn_minor2chan(minor - ISDN_MINOR_CTRL));
                 else
                         retval = count;
                 goto out;