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[Qemu-block] [PATCH 0/7] qcow2 check improvements

From: Vladimir Sementsov-Ogievskiy
Subject: [Qemu-block] [PATCH 0/7] qcow2 check improvements
Date: Fri, 17 Aug 2018 15:22:12 +0300

Hi all!

02, 06: check bdrv_getlength error return code


We've faced the following problem: after host fs corruption, vm images
becomes invalid. And which is interesting, starting qemu-img check on
them led to allocating of the whole RAM and then killing qemu-img by
OOM Killer.

This was due to corrupted l2 entries, which referenced clusters far-far
beyond the end of the qcow2 file.
02 is a generic fix for the bug, 01 is unrelated improvement, 03-07 are
additional info and fixing for such corrupted table entries.

Questions on 02, 06 and 07:
1. Should restrictions be more or less strict?
2. Are there valid cases, when such entries should not be considered as

Vladimir Sementsov-Ogievskiy (7):
  block/qcow2-refcount: fix check_oflag_copied
  block/qcow2-refcount: avoid eating RAM
  block/qcow2-refcount: check_refcounts_l2: refactor compressed case
  block/qcow2-refcount: check_refcounts_l2: reduce ignored overlaps
  block/qcow2-refcount: check_refcounts_l2: split fix_l2_entry_to_zero
  block/qcow2-refcount: fix out-of-file L1 entries to be zero
  block/qcow2-refcount: fix out-of-file L2 entries to be read-as-zero

 block/qcow2-refcount.c | 270 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 219 insertions(+), 51 deletions(-)


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