[PATCH 4.12 28/31] isdn/i4l: fix buffer overflow

Greg Kroah-Hartman
2017-08-03T23:21:41Z

From: Annie Cherkaev <annie.cherk@gmail.com>

commit 9f5af546e6acc30f075828cb58c7f09665033967 upstream.

This fixes a potential buffer overflow in isdn_net.c caused by an
unbounded strcpy.

[ ISDN seems to be effectively unmaintained, and the I4L driver in
particular is long deprecated, but in case somebody uses this..
- Linus ]

Signed-off-by: Jiten Thakkar <jitenmt@gmail.com>
Signed-off-by: Annie Cherkaev <annie.cherk@gmail.com>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/isdn/i4l/isdn_common.c | 1 +
drivers/isdn/i4l/isdn_net.c | 5 ++---
2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/isdn/i4l/isdn_common.c
+++ b/drivers/isdn/i4l/isdn_common.c
@@ -1379,6 +1379,7 @@ isdn_ioctl(struct file *file, uint cmd,
if (arg) {
if (copy_from_user(bname, argp, sizeof(bname) - 1))
return -EFAULT;
+ bname[sizeof(bname)-1] = 0;
} else
return -EINVAL;
ret = mutex_lock_interruptible(&dev->mtx);
--- a/drivers/isdn/i4l/isdn_net.c
+++ b/drivers/isdn/i4l/isdn_net.c
@@ -2611,10 +2611,9 @@ isdn_net_newslave(char *parm)
char newname[10];

if (p) {
- /* Slave-Name MUST not be empty */
- if (!strlen(p + 1))
+ /* Slave-Name MUST not be empty or overflow 'newname' */
+ if (strscpy(newname, p + 1, sizeof(newname)) <= 0)
return NULL;
- strcpy(newname, p + 1);
*p = 0;
/* Master must already exist */
if (!(n = isdn_net_findif(parm)))