Fix nil pointer dereference in node allocation #2764
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When the network allocator starts, it performs two passes of allocation. The first, with existingAddressesOnly set to "true", simply re-allocates any already reserved addresses, which make the local driver state consistent with the state in swarmkit's object store. The second pass then performs any outstanding new allocations, from when the allocator last stopped. Since moby#2725, nodes only have attachments allocated for them if they have a task currently scheduled which requires those networks. This happens after a task is allocated and scheduled. Before this change, it was possible that, if a Task was correctly allocated, but the allocator stopped before the Node was also allocated, during the restore phase, an empty api.NetworkAttachment object was added to the Node's attachments. Then, in the new allocations phase, when trying to process all attachments, we were unconditionally looking at the NetworkAttachment object's Network field, which was nil. This caused a segfault and crash. With this change, we no longer add these errant NetworkAttachment objects to nodes. Signed-off-by: Drew Erny <drew.erny@docker.com>
anshulpundir
approved these changes
Oct 17, 2018
wk8
approved these changes
Oct 17, 2018
Codecov Report
@@ Coverage Diff @@
## master #2764 +/- ##
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Coverage ? 61.8%
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Files ? 134
Lines ? 21867
Branches ? 0
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Hits ? 13514
Misses ? 6901
Partials ? 1452 |
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@anshulpundir @dperny we need this to be backported to the 18.09 branch (if it is not created, I guess it must be created and cherry-picked ?). |
This was referenced Oct 18, 2018
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- What I did
Fix a nil pointer dereference in the
- How I did it
https://www.youtube.com/watch?v=bLHL75H_VEM
When the network allocator starts, it performs two passes of allocation. The first, with existingAddressesOnly set to "true", simply re-allocates any already reserved addresses, which make the local driver state consistent with the state in swarmkit's object store. The second pass then performs any outstanding new allocations, from when the allocator last stopped.
Since #2725, nodes only have attachments allocated for them if they have a task currently scheduled which requires those networks. This happens after a task is allocated and scheduled.
Before this change, it was possible that, if a Task was correctly allocated, but the allocator stopped before the Node was also allocated, during the restore phase, an empty api.NetworkAttachment object was added to the Node's attachments. Then, in the new allocations phase, when trying to process all attachments, we were unconditionally looking at the NetworkAttachment object's Network field, which was nil. This caused a segfault and crash.
With this change, we no longer add these errant NetworkAttachment objects to nodes.
- How to test it
Includes an automated test, which I have verified fails before the change and passes after.
- Description for the changelog
Fix nil pointer dereference that could crash swarmkit.