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: 92c66ee829 ("pds_fwctl: add rpc and query support")
Link: https://patch.msgid.link/r/[email protected]
Cc: [email protected] # v6.15+
Signed-off-by: Heechan Kang <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

drivers/fwctl/pds/main.c

@@ -362,6 +362,9 @@ static void *pdsfc_fw_rpc(struct fwctl_uctx *uctx, enum fwctl_rpc_scope scope,
 	void *out = NULL;
 	int err;
 
+	if (in_len < sizeof(*rpc))
+		return ERR_PTR(-EINVAL);
+
 	err = pdsfc_validate_rpc(pdsfc, rpc, scope);
 	if (err)
 		return ERR_PTR(err);