From 665d7662d15441b4b3e54131a9418a1a198d0d31 Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Wed, 22 Jul 2009 17:39:42 +0200 Subject: [PATCH] USB: usbtmc: sanity checks for DEV_DEP_MSG_IN urbs According to the specifications, an instrument should not return more data in a DEV_DEP_MSG_IN urb than requested. However, some instruments can send more than requested. This could cause the kernel to write the extra data past the end of the buffer provided by read(). Fix this by checking that the value of the TranserSize field is not larger than the urb itself and not larger than the size of the userspace buffer. Also correctly decrement the remaining size of the buffer when userspace read()s more than USBTMC_SIZE_IOBUFFER. Signed-off-by: Guus Sliepen Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/usbtmc.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c index 4f0858f..5bab8e5 100644 --- a/drivers/usb/class/usbtmc.c +++ b/drivers/usb/class/usbtmc.c @@ -369,13 +369,13 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf, { struct usbtmc_device_data *data; struct device *dev; - unsigned long int n_characters; + u32 n_characters; u8 *buffer; int actual; - int done; - int remaining; + size_t done; + size_t remaining; int retval; - int this_part; + size_t this_part; /* Get pointer to private data structure */ data = filp->private_data; @@ -461,6 +461,18 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf, (buffer[6] << 16) + (buffer[7] << 24); + /* Ensure the instrument doesn't lie about it */ + if(n_characters > actual - 12) { + dev_err(dev, "Device lies about message size: %zu > %zu\n", n_characters, actual - 12); + n_characters = actual - 12; + } + + /* Ensure the instrument doesn't send more back than requested */ + if(n_characters > this_part) { + dev_err(dev, "Device returns more than requested: %zu > %zu\n", done + n_characters, done + this_part); + n_characters = this_part; + } + /* Copy buffer to user space */ if (copy_to_user(buf + done, &buffer[12], n_characters)) { /* There must have been an addressing problem */ @@ -471,6 +483,8 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf, done += n_characters; if (n_characters < USBTMC_SIZE_IOBUFFER) remaining = 0; + else + remaining -= n_characters; } /* Update file position value */ -- 2.7.4