USB: w1 ds2490: Fix bug caused by improper use of altsetting array

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@rowland.harvard.edu>
Reported-and-tested-by: syzbot+d65f673b847a1a96cdba@syzkaller.appspotmail.com
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/w1/masters/ds2490.c b/drivers/w1/masters/ds2490.c
index 0f4ecfcdb549..a9fb77585272 100644
--- a/drivers/w1/masters/ds2490.c
+++ b/drivers/w1/masters/ds2490.c
@@ -1016,15 +1016,15 @@ static int ds_probe(struct usb_interface *intf,
         /* 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",
                         iface_desc->desc.bNumEndpoints);