--- /dev/null
+From 224654004ca688af67cec44d9300e8c3f647577c Mon Sep 17 00:00:00 2001
+From: Ian Abbott <abbotti@mev.co.uk>
+Date: Mon, 26 Jun 2006 12:59:17 +0100
+Subject: USB serial ftdi_sio: Prevent userspace DoS (CVE-2006-2936)
+
+This patch limits the amount of outstanding 'write' data that can be
+queued up for the ftdi_sio driver, to prevent userspace DoS attacks (or
+simple accidents) that use up all the system memory by writing lots of
+data to the serial port.
+
+The original patch was by Guillaume Autran, who in turn based it on the
+same mechanism implemented in the 'visor' driver. I (Ian Abbott)
+re-targeted the patch to the latest sources, fixed a couple of errors,
+renamed his new structure members, and updated the implementations of
+the 'write_room' and 'chars_in_buffer' methods to take account of the
+number of outstanding 'write' bytes. It seems to work fine, though at
+low baud rates it is still possible to queue up an amount of data that
+takes an age to shift (a job for another day!).
+
+Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+
+---
+ drivers/usb/serial/ftdi_sio.c | 84 +++++++++++++++++++++++++++++++++++-------
+ 1 file changed, 71 insertions(+), 13 deletions(-)
+
+--- linux-2.6.17.4.orig/drivers/usb/serial/ftdi_sio.c
++++ linux-2.6.17.4/drivers/usb/serial/ftdi_sio.c
+@@ -553,6 +553,10 @@ struct ftdi_private {
+
+ int force_baud; /* if non-zero, force the baud rate to this value */
+ int force_rtscts; /* if non-zero, force RTS-CTS to always be enabled */
++
++ spinlock_t tx_lock; /* spinlock for transmit state */
++ unsigned long tx_outstanding_bytes;
++ unsigned long tx_outstanding_urbs;
+ };
+
+ /* Used for TIOCMIWAIT */
+@@ -626,6 +630,9 @@ static struct usb_serial_driver ftdi_sio
+ #define HIGH 1
+ #define LOW 0
+
++/* number of outstanding urbs to prevent userspace DoS from happening */
++#define URB_UPPER_LIMIT 42
++
+ /*
+ * ***************************************************************************
+ * Utlity functions
+@@ -1156,6 +1163,7 @@ static int ftdi_sio_attach (struct usb_s
+ }
+
+ spin_lock_init(&priv->rx_lock);
++ spin_lock_init(&priv->tx_lock);
+ init_waitqueue_head(&priv->delta_msr_wait);
+ /* This will push the characters through immediately rather
+ than queue a task to deliver them */
+@@ -1372,6 +1380,7 @@ static int ftdi_write (struct usb_serial
+ int data_offset ; /* will be 1 for the SIO and 0 otherwise */
+ int status;
+ int transfer_size;
++ unsigned long flags;
+
+ dbg("%s port %d, %d bytes", __FUNCTION__, port->number, count);
+
+@@ -1379,6 +1388,13 @@ static int ftdi_write (struct usb_serial
+ dbg("write request of 0 bytes");
+ return 0;
+ }
++ spin_lock_irqsave(&priv->tx_lock, flags);
++ if (priv->tx_outstanding_urbs > URB_UPPER_LIMIT) {
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
++ dbg("%s - write limit hit\n", __FUNCTION__);
++ return 0;
++ }
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+ data_offset = priv->write_offset;
+ dbg("data_offset set to %d",data_offset);
+@@ -1445,6 +1461,11 @@ static int ftdi_write (struct usb_serial
+ err("%s - failed submitting write urb, error %d", __FUNCTION__, status);
+ count = status;
+ kfree (buffer);
++ } else {
++ spin_lock_irqsave(&priv->tx_lock, flags);
++ ++priv->tx_outstanding_urbs;
++ priv->tx_outstanding_bytes += count;
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
+ }
+
+ /* we are done with this urb, so let the host driver
+@@ -1460,7 +1481,11 @@ static int ftdi_write (struct usb_serial
+
+ static void ftdi_write_bulk_callback (struct urb *urb, struct pt_regs *regs)
+ {
++ unsigned long flags;
+ struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
++ struct ftdi_private *priv;
++ int data_offset; /* will be 1 for the SIO and 0 otherwise */
++ unsigned long countback;
+
+ /* free up the transfer buffer, as usb_free_urb() does not do this */
+ kfree (urb->transfer_buffer);
+@@ -1472,34 +1497,67 @@ static void ftdi_write_bulk_callback (st
+ return;
+ }
+
++ priv = usb_get_serial_port_data(port);
++ if (!priv) {
++ dbg("%s - bad port private data pointer - exiting", __FUNCTION__);
++ return;
++ }
++ /* account for transferred data */
++ countback = urb->actual_length;
++ data_offset = priv->write_offset;
++ if (data_offset > 0) {
++ /* Subtract the control bytes */
++ countback -= (data_offset * ((countback + (PKTSZ - 1)) / PKTSZ));
++ }
++ spin_lock_irqsave(&priv->tx_lock, flags);
++ --priv->tx_outstanding_urbs;
++ priv->tx_outstanding_bytes -= countback;
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
++
+ schedule_work(&port->work);
+ } /* ftdi_write_bulk_callback */
+
+
+ static int ftdi_write_room( struct usb_serial_port *port )
+ {
++ struct ftdi_private *priv = usb_get_serial_port_data(port);
++ int room;
++ unsigned long flags;
++
+ dbg("%s - port %d", __FUNCTION__, port->number);
+
+- /*
+- * We really can take anything the user throws at us
+- * but let's pick a nice big number to tell the tty
+- * layer that we have lots of free space
+- */
+- return 2048;
++ spin_lock_irqsave(&priv->tx_lock, flags);
++ if (priv->tx_outstanding_urbs < URB_UPPER_LIMIT) {
++ /*
++ * We really can take anything the user throws at us
++ * but let's pick a nice big number to tell the tty
++ * layer that we have lots of free space
++ */
++ room = 2048;
++ } else {
++ room = 0;
++ }
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
++ return room;
+ } /* ftdi_write_room */
+
+
+ static int ftdi_chars_in_buffer (struct usb_serial_port *port)
+ { /* ftdi_chars_in_buffer */
++ struct ftdi_private *priv = usb_get_serial_port_data(port);
++ int buffered;
++ unsigned long flags;
++
+ dbg("%s - port %d", __FUNCTION__, port->number);
+
+- /*
+- * We can't really account for how much data we
+- * have sent out, but hasn't made it through to the
+- * device, so just tell the tty layer that everything
+- * is flushed.
+- */
+- return 0;
++ spin_lock_irqsave(&priv->tx_lock, flags);
++ buffered = (int)priv->tx_outstanding_bytes;
++ spin_unlock_irqrestore(&priv->tx_lock, flags);
++ if (buffered < 0) {
++ err("%s outstanding tx bytes is negative!", __FUNCTION__);
++ buffered = 0;
++ }
++ return buffered;
+ } /* ftdi_chars_in_buffer */
+
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
