fwctl: pds: Validate RPC input size before parsing

fwctl: pds: Validate RPC input size before parsing

The fwctl core allocates the device-specific RPC input buffer with
fwctl_rpc.in_len and passes that buffer to the driver callback.

pdsfc_fw_rpc() casts the buffer to struct fwctl_rpc_pds and then calls
pdsfc_validate_rpc(), which reads fields from that structure before
checking that the input buffer is large enough to contain it. A short
in_len can make pds_fwctl read beyond the allocation.

Reject pds RPC buffers that are smaller than struct fwctl_rpc_pds before
parsing any pds-specific fields.

Fixes: 92c66ee829b9 ("pds_fwctl: add rpc and query support")
Link: https://patch.msgid.link/r/20260517062232.1858747-1-gganji11@naver.com
Cc: stable@vger.kernel.org # v6.15+
Signed-off-by: Heechan Kang <gganji11@naver.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>