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Date: Mon, 07 Feb 2011 14:48:47 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] QCOW2: bug fix - read base image beyond
	its	size
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To: Chunqiang Tang <ctang@us.ibm.com>
Cc: qemu-devel@nongnu.org

Am 03.02.2011 16:12, schrieb Chunqiang Tang:
> This patch fixes the following bug in QCOW2. For a QCOW2 image that is larger
> than its base image, when handling a read request straddling over the end of the
> base image, the QCOW2 driver attempts to read beyond the end of the base image
> and the request would fail.
> 
> This bug was found by Fast Virtual Disk (FVD)'s fully automated testing tool.
> The following test triggered the bug.
> 
> dd if=/dev/zero of=/var/ramdisk/truth.raw count=0 bs=1 seek=1098561536
> dd if=/dev/zero of=/var/ramdisk/zero-500M.raw count=0 bs=1 seek=593099264
> ./qemu-img create -f qcow2 -ocluster_size=65536,backing_fmt=blksim -b /var/ramdisk/zero-500M.raw /var/ramdisk/test.qcow2 1098561536
> ./qemu-io --auto --seed=30477694 --truth=/var/ramdisk/truth.raw --format=qcow2 --test=blksim:/var/ramdisk/test.qcow2 --verify_write=true --compare_before=false --compare_after=true --round=100000 --parallel=100 --io_size=10485760 --fail_prob=0 --cancel_prob=0 --instant_qemubh=true
> 
> Signed-off-by: Chunqiang Tang <ctang@us.ibm.com>

Thanks, fixed up the coding style (whitespace) and applied to the block
branch.

However, I wonder if we can't share some code between
qemu_iovec_memset_skip and qemu_iovec_copy. I think a cleanup patch
would be possible there.

Kevin