[PATCH 5.4 54/72] usblp: fix race between disconnect() and read()

[Greg Kroah-Hartman]

From: Oliver Neukum <oneukum@xxxxxxxx>

commit 9cdabcb3ef8c24ca3a456e4db7b012befb688e73 upstream.

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

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Reported-by: syzbot+be5b5f86a162a6c281e6@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20200917103427.15740-1-oneukum@xxxxxxxx
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/class/usblp.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *f
 	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);