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 f38e7f81d8..28c3a712b6 100644

--- a/block/io.c

+++ b/block/io.c

@@ -1764,6 +1764,10 @@ static int bdrv_pad_request(BlockDriverState *bs,

 {

     int ret;

+    if (!qiov) {

+        return 0;

+    }

+

     bdrv_check_qiov_request(*offset, *bytes, *qiov, *qiov_offset, &error_abort);

     if (!bdrv_init_padding(bs, *offset, *bytes, pad)) {