[PATCH 1/2] usb: usblp: fix heap leak in IEEE 1284 device ID via short response

[PATCH 1/2] usb: usblp: fix heap leak in IEEE 1284 device ID via short response

[Greg Kroah-Hartman]

usblp_ctrl_msg() collapses the usb_control_msg() return value to
0/-errno, discarding the actual number of bytes transferred.  A broken
printer can complete the GET_DEVICE_ID control transfer short and the
driver has no way to know.

usblp_cache_device_id_string() reads the 2-byte big-endian length prefix
from the response and trusts it (clamped only to the buffer bounds).
The buffer is kmalloc(1024) at probe time. A device that sends exactly
two bytes (e.g. 0x03 0xFF, claiming a 1023-byte ID) leaves
device_id_string[2..1022] holding stale kmalloc heap.

That stale data is then exposed:
  - via the ieee1284_id sysfs attribute (sprintf("%s", buf+2), truncated
    at the first NUL in the stale heap), and
  - via the IOCNR_GET_DEVICE_ID ioctl, which copy_to_user()s the full
    claimed length regardless of NULs, up to 1021 bytes of uninitialized
    heap, with the leak size chosen by the device.

Fix this up by just zapping the buffer with zeros before each request
sent to the device.

Cc: Pete Zaitcev <zaitcev@redhat.com>
Assisted-by: gkh_clanker_t1000
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/class/usblp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 669b9e6879bf..e9b848622a3a 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -1377,6 +1377,7 @@ static int usblp_cache_device_id_string(struct usblp *usblp)
 {
 	int err, length;
 
+	memset(usblp->device_id_string, 0, USBLP_DEVICE_ID_SIZE);
 	err = usblp_get_id(usblp, 0, usblp->device_id_string, USBLP_DEVICE_ID_SIZE - 1);
 	if (err < 0) {
 		dev_dbg(&usblp->intf->dev,
-- 
2.53.0

[PATCH 2/2] usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl

[Greg Kroah-Hartman]

Just like in a previous problem in this driver, usblp_ctrl_msg() will
collapse the usb_control_msg() return value to 0/-errno, discarding the
actual number of bytes transferred.

Ideally that short command should be detected and error out, but many
printers are known to send "incorrect" responses back so we can't just
do that.

statusbuf is kmalloc(8) at probe time and never filled before the first
LPGETSTATUS ioctl.

usblp_read_status() requests 1 byte. If a malicious printer responds
with zero bytes, *statusbuf is one byte of stale kmalloc heap,
sign-extended into the local int status, which the LPGETSTATUS path then
copy_to_user()s directly to the ioctl caller.

Fix this all by just zapping out the memory buffer when allocated at
probe time.  If a later call does a short read, the data will be
identical to what the device sent it the last time, so there is no
"leak" of information happening.

Cc: Pete Zaitcev <zaitcev@redhat.com>
Assisted-by: gkh_clanker_t1000
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/class/usblp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index e9b848622a3a..746414763da5 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -1178,7 +1178,7 @@ static int usblp_probe(struct usb_interface *intf,
 	}
 
 	/* Allocate buffer for printer status */
-	usblp->statusbuf = kmalloc(STATUS_BUF_SIZE, GFP_KERNEL);
+	usblp->statusbuf = kzalloc(STATUS_BUF_SIZE, GFP_KERNEL);
 	if (!usblp->statusbuf) {
 		retval = -ENOMEM;
 		goto abort;
-- 
2.53.0