Commit 66c36502 authored Feb 19, 2016 by Ian Abbott Committed by Greg Kroah-Hartman Feb 20, 2016

staging: comedi: COMEDI_BUFINFO: force bytes_read or bytes_written to 0



The `COMEDI_BUFINFO` ioctl is used to advance the current position in
the buffer by a specified amount (which can be 0) and get the new
position.  On input, the `bytes_read` member of `struct comedi_bufinfo`
specifies the amount to advance the "read" position for an asynchronous
command in the "read" direction, and the `bytes_written` member
specifies the amount to advance the "write" position for a command in
the "write" direction.  The handler `do_bufinfo_ioctl()` may adjust
these by the amount the position is actually advanced before copying
them back to the user.  Currently, it ignores the specified `bytes_read`
value for a command in the "write" direction, and ignores the specified
`bytes_written` for a command in the "read" direction, so the values
copied back to the user are unchanged.  Change it to force the ignored
value to 0 before copying the values back to the user.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent e5be74c7

drivers/staging/comedi/comedi_fops.c

+18 −12

Original line number	Diff line number	Diff line
		@@ -1141,19 +1141,25 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
		if (s->busy != file)
		return -EACCES;

		if (bi.bytes_read && !(async->cmd.flags & CMDF_WRITE)) {
		if (!(async->cmd.flags & CMDF_WRITE)) {
		/* command was set up in "read" direction */
		if (bi.bytes_read) {
		comedi_buf_read_alloc(s, bi.bytes_read);
		bi.bytes_read = comedi_buf_read_free(s, bi.bytes_read);

		if (comedi_is_subdevice_idle(s) &&
		comedi_buf_read_n_available(s) == 0) {
		comedi_buf_read_n_available(s) == 0)
		do_become_nonbusy(dev, s);
		}
		}

		if (bi.bytes_written && (async->cmd.flags & CMDF_WRITE)) {
		bi.bytes_written = 0;
		} else {
		/* command was set up in "write" direction */
		if (bi.bytes_written) {
		comedi_buf_write_alloc(s, bi.bytes_written);
		bi.bytes_written = comedi_buf_write_free(s, bi.bytes_written);
		bi.bytes_written =
		comedi_buf_write_free(s, bi.bytes_written);
		}
		bi.bytes_read = 0;
		}

		copyback_position: