[PATCH 4.19 14/99] USB: w1 ds2490: Fix bug caused by improper use of altsetting array

From: Greg Kroah-Hartman
Date: Mon May 06 2019 - 10:40:08 EST

From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

commit c114944d7d67f24e71562fcfc18d550ab787e4d4 upstream.

The syzkaller USB fuzzer spotted a slab-out-of-bounds bug in the
ds2490 driver. This bug is caused by improper use of the altsetting
array in the usb_interface structure (the array's entries are not
always stored in numerical order), combined with a naive assumption
that all interfaces probed by the driver will have the expected number
of altsettings.

The bug can be fixed by replacing references to the possibly
non-existent intf->altsetting[alt] entry with the guaranteed-to-exist
intf->cur_altsetting entry.

Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Reported-and-tested-by: syzbot+d65f673b847a1a96cdba@xxxxxxxxxxxxxxxxxxxxxxxxx
CC: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/w1/masters/ds2490.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/w1/masters/ds2490.c
+++ b/drivers/w1/masters/ds2490.c
@@ -1016,15 +1016,15 @@ static int ds_probe(struct usb_interface
/* alternative 3, 1ms interrupt (greatly speeds search), 64 byte bulk */
alt = 3;
err = usb_set_interface(dev->udev,
- intf->altsetting[alt].desc.bInterfaceNumber, alt);
+ intf->cur_altsetting->desc.bInterfaceNumber, alt);
if (err) {
dev_err(&dev->udev->dev, "Failed to set alternative setting %d "
"for %d interface: err=%d.\n", alt,
- intf->altsetting[alt].desc.bInterfaceNumber, err);
+ intf->cur_altsetting->desc.bInterfaceNumber, err);
goto err_out_clear;

- iface_desc = &intf->altsetting[alt];
+ iface_desc = intf->cur_altsetting;
if (iface_desc->desc.bNumEndpoints != NUM_EP-1) {
pr_info("Num endpoints=%d. It is not DS9490R.\n",