misc: fastrpc: fix improper packet size calculation

The buffer list is sorted and this is not being considered while
calculating packet size. This would lead to improper copy length
calculation for non-dmaheap buffers which would eventually cause
sending improper buffers to DSP.

Fixes: c68cfb718c ("misc: fastrpc: Add support for context Invoke method")
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Jeya R <jeyr@codeaurora.org>
Link: https://lore.kernel.org/r/1637771481-4299-1-git-send-email-jeyr@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -719,16 +719,18 @@ static int fastrpc_get_meta_size(struct fastrpc_invoke_ctx *ctx)
 static u64 fastrpc_get_payload_size(struct fastrpc_invoke_ctx *ctx, int metalen)
 {
 	u64 size = 0;
-	int i;
+	int oix;
 
 	size = ALIGN(metalen, FASTRPC_ALIGN);
-	for (i = 0; i < ctx->nscalars; i++) {
+	for (oix = 0; oix < ctx->nbufs; oix++) {
+		int i = ctx->olaps[oix].raix;
+
 		if (ctx->args[i].fd == 0 || ctx->args[i].fd == -1) {
 
-			if (ctx->olaps[i].offset == 0)
+			if (ctx->olaps[oix].offset == 0)
 				size = ALIGN(size, FASTRPC_ALIGN);
 
-			size += (ctx->olaps[i].mend - ctx->olaps[i].mstart);
+			size += (ctx->olaps[oix].mend - ctx->olaps[oix].mstart);
 		}
 	}