Patchwork [PULL,03/30] qcow2: Unset zero_beyond_eof in save_vmstate

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Submitter Kevin Wolf
Date Oct. 31, 2013, 3:48 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/287523/
State New
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Kevin Wolf - Oct. 31, 2013, 3:48 p.m.
From: Max Reitz <>

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 <>
Reviewed-by: Eric Blake <>
Signed-off-by: Kevin Wolf <>
 block/qcow2.c | 3 +++
 1 file changed, 3 insertions(+)


diff --git a/block/qcow2.c b/block/qcow2.c
index 4a3e8b4..01269f9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -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;
     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