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USB: serial: mct_u232: fix memory corruption with small endpoint

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The driver overrides the maximum transfer size for a specific device
which only accepts 16 byte packets for its 32 byte bulk-out endpoint.

Make sure to never increase the maximum transfer size to prevent slab
corruption should a malicious device report a smaller endpoint max
packet size than expected.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2026-05-20 16:27:00 +02:00
parent ab8336a7e4
commit 915b36d701
1 changed files with 11 additions and 10 deletions
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21
drivers/usb/serial/mct_u232.c
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@ -378,6 +378,7 @@ static int mct_u232_port_probe(struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
struct mct_u232_private *priv;
u16 pid;
/* check first to simplify error handling */
if (!serial->port[1] || !serial->port[1]->interrupt_in_urb) {
@ -385,6 +386,16 @@ static int mct_u232_port_probe(struct usb_serial_port *port)
return -ENODEV;
}
/*
* Compensate for a hardware bug: although the Sitecom U232-P25
* device reports a maximum output packet size of 32 bytes,
* it seems to be able to accept only 16 bytes (and that's what
* SniffUSB says too...)
*/
pid = le16_to_cpu(serial->dev->descriptor.idProduct);
if (pid == MCT_U232_SITECOM_PID)
port->bulk_out_size = min(16, port->bulk_out_size);
priv = kzalloc_obj(*priv);
if (!priv)
return -ENOMEM;
@ -410,7 +421,6 @@ static void mct_u232_port_remove(struct usb_serial_port *port)
static int mct_u232_open(struct tty_struct *tty, struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
struct mct_u232_private *priv = usb_get_serial_port_data(port);
int retval = 0;
unsigned int control_state;
@ -418,15 +428,6 @@ static int mct_u232_open(struct tty_struct *tty, struct usb_serial_port *port)
unsigned char last_lcr;
unsigned char last_msr;
/* Compensate for a hardware bug: although the Sitecom U232-P25
* device reports a maximum output packet size of 32 bytes,
* it seems to be able to accept only 16 bytes (and that's what
* SniffUSB says too...)
*/
if (le16_to_cpu(serial->dev->descriptor.idProduct)
== MCT_U232_SITECOM_PID)
port->bulk_out_size = 16;
/* Do a defined restart: the normal serial device seems to
* always turn on DTR and RTS here, so do the same. I'm not
* sure if this is really necessary. But it should not harm