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From e246af75817264aa340cc4e8bb42c17a2d48cbb7 Mon Sep 17 00:00:00 2001
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From: Stefan Weil <sw@weilnetz.de>
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Date: Sat, 21 Jan 2012 13:54:24 +0100
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Subject: [PATCH] block/vdi: Zero unused parts when allocating a new block
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(fix #919242)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The new block was filled with zero when it was allocated by g_malloc0,
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but when it was reused later and only partially used, data from the
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previously allocated block were still present and written to the new
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block.
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This caused the problems reported by bug #919242
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(https://bugs.launchpad.net/qemu/+bug/919242).
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Now the unused parts of the new block which are before and after the data
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are always filled with zero, so it is no longer necessary to zero the whole
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block with g_malloc0.
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I also updated the copyright comment.
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Signed-off-by: Stefan Weil <sw@weilnetz.de>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 641543b76b82a8b361482b727e08de0c8ec093b0)
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[AF: g_malloc() -> qemu_malloc()]
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Signed-off-by: Andreas Färber <afaerber@suse.de>
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---
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block/vdi.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/block/vdi.c b/block/vdi.c
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index 1be0cdc..07413af 100644
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--- a/block/vdi.c
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+++ b/block/vdi.c
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@@ -1,7 +1,7 @@
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/*
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* Block driver for the Virtual Disk Image (VDI) format
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*
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- * Copyright (c) 2009 Stefan Weil
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+ * Copyright (c) 2009, 2012 Stefan Weil
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@@ -765,15 +765,19 @@ static void vdi_aio_write_cb(void *opaque, int ret)
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(uint64_t)bmap_entry * s->block_sectors;
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block = acb->block_buffer;
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if (block == NULL) {
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- block = qemu_mallocz(s->block_size);
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+ block = qemu_malloc(s->block_size);
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acb->block_buffer = block;
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acb->bmap_first = block_index;
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assert(!acb->header_modified);
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acb->header_modified = 1;
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}
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acb->bmap_last = block_index;
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+ /* Copy data to be written to new block and zero unused parts. */
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+ memset(block, 0, sector_in_block * SECTOR_SIZE);
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memcpy(block + sector_in_block * SECTOR_SIZE,
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acb->buf, n_sectors * SECTOR_SIZE);
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+ memset(block + (sector_in_block + n_sectors) * SECTOR_SIZE, 0,
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+ (s->block_sectors - n_sectors - sector_in_block) * SECTOR_SIZE);
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acb->hd_iov.iov_base = (void *)block;
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acb->hd_iov.iov_len = s->block_size;
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qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);
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--
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1.7.11.2
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