From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Stefan Reiter <s.reiter@proxmox.com>
Date: Tue, 2 Mar 2021 16:11:54 +0100
Subject: [PATCH] block/io: accept NULL qiov in bdrv_pad_request

Some operations, e.g. block-stream, perform reads while discarding the
results (only copy-on-read matters). In this case they will pass NULL as
the target QEMUIOVector, which will however trip bdrv_pad_request, since
it wants to extend its passed vector.

Simply check for NULL and do nothing, there's no reason to pad the
target if it will be discarded anyway.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 block/io.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/io.c b/block/io.c
index 83d1b1dfdc..24a3c84c93 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1710,6 +1710,10 @@ static int bdrv_pad_request(BlockDriverState *bs,
     int sliced_niov;
     size_t sliced_head, sliced_tail;
 
+    if (!qiov) {
+        return 0;
+    }
+
     /* Should have been checked by the caller already */
     ret = bdrv_check_request32(*offset, *bytes, *qiov, *qiov_offset);
     if (ret < 0) {
