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Fix a use-after-free crash when returning from the alt buffer #10878

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Aug 5, 2021

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j4james
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@j4james j4james commented Aug 5, 2021

Summary of the Pull Request

When switching from the alt buffer back to the main buffer, we need to copy certain cursor attributes from the one to the other. However, this copying was taking place after the alt buffer had been freed, and thus could result in the app crashing. This PR simply moves that code up a bit so it's prior to the buffer being freed.

References

PR #10843 added the code that introduced this problem.

PR Checklist

  • Closes #xxx
  • CLA signed.
  • Tests added/passed
  • Documentation updated.
  • Schema updated.
  • I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Validation Steps Performed

I was able to reproduce the crash when using a debug build, and confirmed that the crash no longer occurred after this PR was applied. I also checked that the cursor attributes were still being correctly copied back when returning from the alt buffer.

@zadjii-msft zadjii-msft added AutoMerge Marked for automatic merge by the bot when requirements are met Needs-Second It's a PR that needs another sign-off labels Aug 5, 2021
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ghost commented Aug 5, 2021

Hello @zadjii-msft!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

Do note that I've been instructed to only help merge pull requests of this repository that have been opened for at least 8 hours, a condition that will be fulfilled in about 22 minutes. No worries though, I will be back when the time is right! 😉

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@ghost ghost merged commit 2bd4670 into microsoft:main Aug 5, 2021
DHowett pushed a commit that referenced this pull request Aug 25, 2021
## Summary of the Pull Request

When switching from the alt buffer back to the main buffer, we need to copy certain cursor attributes from the one to the other. However, this copying was taking place after the alt buffer had been freed, and thus could result in the app crashing. This PR simply moves that code up a bit so it's prior to the buffer being freed.

## References

PR #10843 added the code that introduced this problem.

## PR Checklist
* [ ] Closes #xxx
* [x] CLA signed.
* [ ] Tests added/passed
* [ ] Documentation updated.
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

## Validation Steps Performed

I was able to reproduce the crash when using a debug build, and confirmed that the crash no longer occurred after this PR was applied. I also checked that the cursor attributes were still being correctly copied back when returning from the alt buffer.
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ghost commented Aug 31, 2021

🎉Windows Terminal Preview v1.10.2383.0 has been released which incorporates this pull request.:tada:

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ghost commented Aug 31, 2021

🎉Windows Terminal Preview v1.11.2421.0 has been released which incorporates this pull request.:tada:

Handy links:

@j4james j4james deleted the fix-altbuffer-crash branch September 26, 2021 15:56
This pull request was closed.
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3 participants