VM: Fix segfault during shutdown of socket listening registry

The following happened:

A listening socket (ipv4, first-port) was created.  Afterwards another
listening socket (ipv6, 0) is being created.  We look up in the hashmap
if there is already a listening socket on port `0` (which is never the case).
So we create a new socket, the OS assigns the socket a random port
(which just happens to be `first-port` as well).  Then we insert a new OSSocket
entry into the hashmap with key `first-port` (and set its `next` field to NULL).
This will simply override the existing entry.

During shutdown we loop over all (fd, OSSocket) pairs and try to remove
`OSSocket` from the port->socket map (via the linked `next` list).  We cannot
find the `OSSocket` which we accidentally droped earlier, so we dereference
`0->next` and hit a SEGFAULT.

What should've happend is to correctly link the `OSSocket`s via the next field.

Fixes #27847

R=asiva@google.com, fschneider@google.com

Review URL: https://codereview.chromium.org/2540013002 .
1 file changed
tree: 0d56332a56043766ab8611a0c0197d1d2ff015b5
  1. build/
  2. client/
  3. docs/
  4. pkg/
  5. runtime/
  6. samples/
  7. samples-dev/
  8. sdk/
  9. tests/
  10. third_party/
  11. tools/
  12. utils/
  13. .clang-format
  14. .gitattributes
  15. .gitignore
  16. .gn
  17. .mailmap
  18. .packages
  19. .travis.yml
  21. BUILD.gn
  22. CHANGELOG.md
  23. codereview.settings
  24. create_sdk.gyp
  25. dart.gyp
  26. DEPS
  29. PRESUBMIT.py
  30. README.dart-sdk
  31. README.md


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