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

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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>
This commit is contained in:
Ian Abbott 2016-02-19 16:13:51 +00:00 committed by Greg Kroah-Hartman
parent e5be74c7c2
commit 66c365026b
1 changed files with 17 additions and 11 deletions
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28
drivers/staging/comedi/comedi_fops.c
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@ -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)) {
comedi_buf_read_alloc(s, bi.bytes_read);
bi.bytes_read = comedi_buf_read_free(s, bi.bytes_read);
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) {
do_become_nonbusy(dev, s);
if (comedi_is_subdevice_idle(s) &&
comedi_buf_read_n_available(s) == 0)
do_become_nonbusy(dev, s);
}
}
if (bi.bytes_written && (async->cmd.flags & CMDF_WRITE)) {
comedi_buf_write_alloc(s, bi.bytes_written);
bi.bytes_written = comedi_buf_write_free(s, bi.bytes_written);
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_read = 0;
}
copyback_position: