OPENAFS-SA-2024-003: sys: Don't over-copy RMTSYS_Pioctl output data

OPENAFS-SA-2024-003: sys: Don't over-copy RMTSYS_Pioctl output data

CVE-2024-10397

Here, 'OutData' only has OutData.rmtbulk_len bytes in it. We know that
OutData.rmtbulk_len is at most data->out_size, but it could be
smaller. So, only copy OutData.rmtbulk_len bytes, not data->out_size,
since data->out_size could be more than the number of bytes we have
allocated in OutData.

FIXES 135043

Reviewed-on: https://gerrit.openafs.org/15924
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit f31a79d749abc8e64a8d9ac748bb2b5457875099)

Change-Id: Ic05751d05c7c8862770188131110cc602c9b93b7
Reviewed-on: https://gerrit.openafs.org/15946
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>