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qcow2: Unset zero_beyond_eof in save_vmstate 

Saving the VM state is done using bdrv_pwrite. This function may perform
a read-modify-write, which in this case results in data being read from
beyond the end of the virtual disk. Since we are actually trying to
access an area which is not a part of the virtual disk, zero_beyond_eof
has to be set to false before performing the partial write, otherwise
the VM state may become corrupted.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2013-10-20 21:52:35 +02:00 committed by Kevin Wolf
parent eedff66f21
commit 6e13610aa4
1 changed files with 3 additions and 0 deletions
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block/qcow2.c
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@ -1941,12 +1941,15 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
BDRVQcowState *s = bs->opaque;
int64_t total_sectors = bs->total_sectors;
int growable = bs->growable;
bool zero_beyond_eof = bs->zero_beyond_eof;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
bs->growable = 1;
bs->zero_beyond_eof = false;
ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
bs->growable = growable;
bs->zero_beyond_eof = zero_beyond_eof;
/* bdrv_co_do_writev will have increased the total_sectors value to include
* the VM state - the VM state is however not an actual part of the block