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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Oliver Neukum <oneukum@suse.com>,
        syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
Subject: [PATCH 5.8 088/118] usblp: fix race between disconnect() and read()
Date:   Mon, 21 Sep 2020 18:28:20 +0200
Message-Id: <20200921162040.443193883@linuxfoundation.org>
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From: Oliver Neukum <oneukum@suse.com>

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@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>
---
 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);