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Fix #5808: Handle possible dangling reference safely #5812

Merged
merged 4 commits into from
Jun 28, 2023
Merged

Fix #5808: Handle possible dangling reference safely #5812

merged 4 commits into from
Jun 28, 2023

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matheus-consoli
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Attempts to fix #5808.

Motivation

Handle Notify as a possible dangling reference to avoid Undefined Behavior.

Technically, this is not UB today because Notify uses an UnsafeCell internally, which prevents the problem with the pointer aliasing rules based on https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html.

Solution

Wrap the reference holder with a MaybeUninit.

@github-actions github-actions bot added the R-loom Run loom tests on this PR label Jun 22, 2023
@Darksonn Darksonn added A-tokio-util Area: The tokio-util crate M-sync Module: tokio/sync labels Jun 23, 2023
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Darksonn reviewed Jun 23, 2023
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Thank you for the PR.

tokio-util/src/sync/cancellation_token.rs Outdated Show resolved Hide resolved
tokio-util/src/sync/cancellation_token.rs Outdated Show resolved Hide resolved
@matheus-consoli matheus-consoli changed the title Fix #5080: Handle possible dangling reference safely Fix #5008: Handle possible dangling reference safely Jun 24, 2023
@matheus-consoli matheus-consoli changed the title Fix #5008: Handle possible dangling reference safely Fix #5808: Handle possible dangling reference safely Jun 24, 2023
@matheus-consoli matheus-consoli force-pushed the 5808-maybedangling branch 2 times, most recently from 9c61198 to eac9b92 Compare June 27, 2023 21:17
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Darksonn approved these changes Jun 28, 2023
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Thanks. Looks good to me.

@Darksonn Darksonn merged commit 1bfe778 into tokio-rs:master Jun 28, 2023
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@matheus-consoli matheus-consoli deleted the 5808-maybedangling branch June 28, 2023 14:53
@cconstantine cconstantine mentioned this pull request Sep 20, 2023
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A-tokio-util Area: The tokio-util crate M-sync Module: tokio/sync R-loom Run loom tests on this PR
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WaitForCancellationFutureOwned should use MaybeUninit
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