From 438061ed1ad85e6743e2dce826671772d81089ec Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Fri, 22 May 2026 16:22:18 +0200 Subject: [PATCH] USB: serial: safe_serial: fix memory corruption with small endpoint Make sure that the bulk-out buffer size is at least eight bytes to avoid user-controlled slab corruption in "safe" mode should a malicious device report a smaller size. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold --- drivers/usb/serial/safe_serial.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/usb/serial/safe_serial.c b/drivers/usb/serial/safe_serial.c index 238b54993446..d267a31dcccf 100644 --- a/drivers/usb/serial/safe_serial.c +++ b/drivers/usb/serial/safe_serial.c @@ -259,6 +259,7 @@ static int safe_prepare_write_buffer(struct usb_serial_port *port, static int safe_startup(struct usb_serial *serial) { struct usb_interface_descriptor *desc; + int bulk_out_size; if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS) return -ENODEV; @@ -279,6 +280,16 @@ static int safe_startup(struct usb_serial *serial) default: return -EINVAL; } + + /* + * The bulk-out buffer needs to be large enough for the two-byte + * trailer in safe mode, but assume anything smaller than eight bytes + * is broken. + */ + bulk_out_size = serial->port[0]->bulk_out_size; + if (bulk_out_size > 0 && bulk_out_size < 8) + return -EINVAL; + return 0; }