[Qemu-devel] [Bug 1592590] [NEW] Prevent qemu-img resize from causing "Active L1 table too large"

[Nowaker]

Public bug reported:

This commit prevents qemu from overallocating if qcow2 image is too big
(whatever that means): https://lists.gnu.org/archive/html/qemu-
devel/2014-07/msg01481.html

However, `qemu-img resize` isn't protected by the same code and allows
to go beyond that.

address@hidden ~virtkick/hdd # qemu-img resize 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2 +100000T
Image resized.

Which then causes "Active L1 table too large" error that cannot be
reversed.

address@hidden ~virtkick/hdd # qemu-img info 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2
qemu-img: Could not open '33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2': 
Active L1 table too large

address@hidden ~virtkick/hdd # qemu-img resize 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2 -100000T
qemu-img: Could not open '33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2': 
Active L1 table too large


I originally faces this bug when I passed wrong parameters to qemu-img in a 
programatic way which caused an image to go corrupt. It's good to protect 
user's images from being resized too much.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: qemu-img

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https://bugs.launchpad.net/bugs/1592590

Title:
  Prevent qemu-img resize from causing "Active L1 table too large"

Status in QEMU:
  New

Bug description:
  This commit prevents qemu from overallocating if qcow2 image is too
  big (whatever that means): https://lists.gnu.org/archive/html/qemu-
  devel/2014-07/msg01481.html

  However, `qemu-img resize` isn't protected by the same code and allows
  to go beyond that.

  address@hidden ~virtkick/hdd # qemu-img resize 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2 +100000T
  Image resized.

  Which then causes "Active L1 table too large" error that cannot be
  reversed.

  address@hidden ~virtkick/hdd # qemu-img info 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2
  qemu-img: Could not open 
'33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2': Active L1 table too large

  address@hidden ~virtkick/hdd # qemu-img resize 
33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2 -100000T
  qemu-img: Could not open 
'33_test_609dffde-eb51-4b75-918d-b814f1bcb526.qcow2': Active L1 table too large

  
  I originally faces this bug when I passed wrong parameters to qemu-img in a 
programatic way which caused an image to go corrupt. It's good to protect 
user's images from being resized too much.

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