misc: fastrpc: Free DMA handles for RPC calls with no arguments

The FDs for DMA handles to be freed is updated in fdlist by DSP over
a remote call. This holds true even for remote calls with no
arguments. To handle this, get_args and put_args are needed to
be called for remote calls with no arguments also as fdlist
is allocated in get_args and FDs updated in fdlist is freed
in put_args.

Fixes: 8f6c1d8 ("misc: fastrpc: Add fdlist implementation")
Cc: stable <stable@kernel.org>
Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20231013122007.174464-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ekansh Gupta

drivers/misc/fastrpc.c

@@ -1091,6 +1091,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
 		}
 	}
 
+	/* Clean up fdlist which is updated by DSP */
 	for (i = 0; i < FASTRPC_MAX_FDLIST; i++) {
 		if (!fdlist[i])
 			break;
@@ -1157,11 +1158,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
-	if (ctx->nscalars) {
-		err = fastrpc_get_args(kernel, ctx);
-		if (err)
-			goto bail;
-	}
+	err = fastrpc_get_args(kernel, ctx);
+	if (err)
+		goto bail;
 
 	/* make sure that all CPU memory writes are seen by DSP */
 	dma_wmb();
@@ -1185,14 +1184,12 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	if (err)
 		goto bail;
 
-	if (ctx->nscalars) {
-		/* make sure that all memory writes by DSP are seen by CPU */
-		dma_rmb();
-		/* populate all the output buffers with results */
-		err = fastrpc_put_args(ctx, kernel);
-		if (err)
-			goto bail;
-	}
+	/* make sure that all memory writes by DSP are seen by CPU */
+	dma_rmb();
+	/* populate all the output buffers with results */
+	err = fastrpc_put_args(ctx, kernel);
+	if (err)
+		goto bail;
 
 bail:
 	if (err != -ERESTARTSYS && err != -ETIMEDOUT) {