usblp: fix race between disconnect() and read()

read() needs to check whether the device has been
disconnected before it tries to talk to the device.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20200917103427.15740-1-oneukum@suse.com
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 084c48c..67cbd42 100644 (file)
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
        if (rv < 0)
                return rv;
 
+       if (!usblp->present) {
+               count = -ENODEV;
+               goto done;
+       }
+
        if ((avail = usblp->rstatus) < 0) {
                printk(KERN_ERR "usblp%d: error %d reading from printer\n",
                    usblp->minor, (int)avail);