usb: core: fix slab-out-of-bounds Read in read_descriptors

commit a18cd6c9b6bc73dc17e8b7e9bd07decaa8833c97 upstream.

The USB device descriptor may get changed between two consecutive
enumerations on the same device for some reason, such as DFU or
malicius device.
In that case, we may access the changing descriptor if we don't take
the device lock here.

The issue is reported:
https://syzkaller.appspot.com/bug?id=901a0d9e6519ef8dc7acab25344bd287dd3c7be9

Cc: stable <stable@vger.kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Reported-by: syzbot+256e56ddde8b8957eabd@syzkaller.appspotmail.com
Fixes: 217a9081d8e6 ("USB: add all configs to the "descriptors" attribute")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Link: https://lore.kernel.org/r/1599201467-11000-1-git-send-email-prime.zeng@hisilicon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 15c19863f7b34a49a6c3118347322ea5b5309348..e97834c3509224e5295b70fda9a887eed2dc015a 100644 (file)
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -865,7 +865,11 @@ read_descriptors(struct file *filp, struct kobject *kobj,
        size_t srclen, n;
        int cfgno;
        void *src;
+       int retval;
 
+       retval = usb_lock_device_interruptible(udev);
+       if (retval < 0)
+               return -EINTR;
        /* The binary attribute begins with the device descriptor.
         * Following that are the raw descriptor entries for all the
         * configurations (config plus subsidiary descriptors).
@@ -890,6 +894,7 @@ read_descriptors(struct file *filp, struct kobject *kobj,
                        off -= srclen;
                }
        }
+       usb_unlock_device(udev);
        return count - nleft;
 }