This is a note to let you know that I've just added the patch titled

USB: usblcd: fix I/O after disconnect

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From eb7f5a490c5edfe8126f64bc58b9ba2edef0a425 Mon Sep 17 00:00:00 2001

From: Johan Hovold johan@kernel.org Date: Thu, 26 Sep 2019 11:12:25 +0200 Subject: USB: usblcd: fix I/O after disconnect

Make sure to stop all I/O on disconnect by adding a disconnected flag which is used to prevent new I/O from being started and by stopping all ongoing I/O before returning.

This also fixes a potential use-after-free on driver unbind in case the driver data is freed before the completion handler has run.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable stable@vger.kernel.org # 7bbe990c989e Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20190926091228.24634-7-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/misc/usblcd.c | 33 +++++++++++++++++++++++++++++++-- 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c index 9ba4a4e68d91..aa982d3ca36b 100644 --- a/drivers/usb/misc/usblcd.c +++ b/drivers/usb/misc/usblcd.c @@ -18,6 +18,7 @@ #include <linux/slab.h> #include <linux/errno.h> #include <linux/mutex.h> +#include <linux/rwsem.h> #include <linux/uaccess.h> #include <linux/usb.h>

@@ -57,6 +58,8 @@ struct usb_lcd { using up all RAM */ struct usb_anchor submitted; /* URBs to wait for before suspend */ + struct rw_semaphore io_rwsem; + unsigned long disconnected:1; }; #define to_lcd_dev(d) container_of(d, struct usb_lcd, kref)

@@ -142,6 +145,13 @@ static ssize_t lcd_read(struct file *file, char __user * buffer,

dev = file->private_data;

+ down_read(&dev->io_rwsem); + + if (dev->disconnected) { + retval = -ENODEV; + goto out_up_io; + } + /* do a blocking bulk read to get data from the device */ retval = usb_bulk_msg(dev->udev, usb_rcvbulkpipe(dev->udev, @@ -158,6 +168,9 @@ static ssize_t lcd_read(struct file *file, char __user * buffer, retval = bytes_read; }

+out_up_io: + up_read(&dev->io_rwsem); + return retval; }

@@ -237,11 +250,18 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, if (r < 0) return -EINTR;

+ down_read(&dev->io_rwsem); + + if (dev->disconnected) { + retval = -ENODEV; + goto err_up_io; + } + /* create a urb, and a buffer for it, and copy the data to the urb */ urb = usb_alloc_urb(0, GFP_KERNEL); if (!urb) { retval = -ENOMEM; - goto err_no_buf; + goto err_up_io; }

buf = usb_alloc_coherent(dev->udev, count, GFP_KERNEL, @@ -278,6 +298,7 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, the USB core will eventually free it entirely */ usb_free_urb(urb);

+ up_read(&dev->io_rwsem); exit: return count; error_unanchor: @@ -285,7 +306,8 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, error: usb_free_coherent(dev->udev, count, buf, urb->transfer_dma); usb_free_urb(urb); -err_no_buf: +err_up_io: + up_read(&dev->io_rwsem); up(&dev->limit_sem); return retval; } @@ -325,6 +347,7 @@ static int lcd_probe(struct usb_interface *interface,

kref_init(&dev->kref); sema_init(&dev->limit_sem, USB_LCD_CONCURRENT_WRITES); + init_rwsem(&dev->io_rwsem); init_usb_anchor(&dev->submitted);

dev->udev = usb_get_dev(interface_to_usbdev(interface)); @@ -422,6 +445,12 @@ static void lcd_disconnect(struct usb_interface *interface) /* give back our minor */ usb_deregister_dev(interface, &lcd_class);

+ down_write(&dev->io_rwsem); + dev->disconnected = 1; + up_write(&dev->io_rwsem); + + usb_kill_anchored_urbs(&dev->submitted); + /* decrement our usage count */ kref_put(&dev->kref, lcd_delete);