crossbeam-channel: prevent double free on Drop#1187
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taiki-e merged 1 commit intocrossbeam-rs:masterfrom Apr 8, 2025
Merged
crossbeam-channel: prevent double free on Drop#1187taiki-e merged 1 commit intocrossbeam-rs:masterfrom
Drop#1187taiki-e merged 1 commit intocrossbeam-rs:masterfrom
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This PR is fixing a regression introduced by crossbeam-rs#1084 that can lead to a double free when dropping the channel. The method `Channel::discard_all_messages` has the property that if it observes `head.block` pointing to a non-null pointer it will attempt to free it. The same property holds for the `Channel::drop` method and so it is critical that whenever `head.block` is freed it must also be set to a null pointer so that it is freed exactly once. Before crossbeam-rs#1084 the behavior of `discard_all_messages` ensured `head.block` was `null` after its execution due to the atomic store right before exiting [1]. After crossbeam-rs#1084 `discard_all_messages` atomically swaps the current value of `head.block` with a null pointer at the moment the value is read instead of waiting for the end of the function. The problem lies in the fact that `dicard_all_messages` contained two paths that could lead to `head.block` being read but only one of them would swap the value. This meant that `dicard_all_messages` could end up observing a non-null block pointer (and therefore attempting to free it) without setting `head.block` to null. This would then lead to `Channel::drop` making a second attempt at dropping the same pointer. The bug is similar to the one previously fixed by crossbeam-rs#972 and the double free can be reproduced by reverting the reproduction commit from that PR [2]. As with crossbeam-rs#972 it is quite difficult to trigger this bug without introducing artificial sleeps in critical points so this PR does not include a test. [1] https://github.com/crossbeam-rs/crossbeam/blob/crossbeam-channel-0.5.11/crossbeam-channel/src/flavors/list.rs#L625 [2] crossbeam-rs@2d22628 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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This PR is fixing a regression introduced by #1084 that can lead to a double free when dropping the channel. The method `Channel::discard_all_messages` has the property that if it observes `head.block` pointing to a non-null pointer it will attempt to free it. The same property holds for the `Channel::drop` method and so it is critical that whenever `head.block` is freed it must also be set to a null pointer so that it is freed exactly once. Before #1084 the behavior of `discard_all_messages` ensured `head.block` was `null` after its execution due to the atomic store right before exiting [1]. After #1084 `discard_all_messages` atomically swaps the current value of `head.block` with a null pointer at the moment the value is read instead of waiting for the end of the function. The problem lies in the fact that `dicard_all_messages` contained two paths that could lead to `head.block` being read but only one of them would swap the value. This meant that `dicard_all_messages` could end up observing a non-null block pointer (and therefore attempting to free it) without setting `head.block` to null. This would then lead to `Channel::drop` making a second attempt at dropping the same pointer. The bug is similar to the one previously fixed by #972 and the double free can be reproduced by reverting the reproduction commit from that PR [2]. As with #972 it is quite difficult to trigger this bug without introducing artificial sleeps in critical points so this PR does not include a test. [1] https://github.com/crossbeam-rs/crossbeam/blob/crossbeam-channel-0.5.11/crossbeam-channel/src/flavors/list.rs#L625 [2] 2d22628 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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This PR is fixing a regression introduced by #1084 that can lead to a double free when dropping the channel. The method `Channel::discard_all_messages` has the property that if it observes `head.block` pointing to a non-null pointer it will attempt to free it. The same property holds for the `Channel::drop` method and so it is critical that whenever `head.block` is freed it must also be set to a null pointer so that it is freed exactly once. Before #1084 the behavior of `discard_all_messages` ensured `head.block` was `null` after its execution due to the atomic store right before exiting [1]. After #1084 `discard_all_messages` atomically swaps the current value of `head.block` with a null pointer at the moment the value is read instead of waiting for the end of the function. The problem lies in the fact that `dicard_all_messages` contained two paths that could lead to `head.block` being read but only one of them would swap the value. This meant that `dicard_all_messages` could end up observing a non-null block pointer (and therefore attempting to free it) without setting `head.block` to null. This would then lead to `Channel::drop` making a second attempt at dropping the same pointer. The bug is similar to the one previously fixed by #972 and the double free can be reproduced by reverting the reproduction commit from that PR [2]. As with #972 it is quite difficult to trigger this bug without introducing artificial sleeps in critical points so this PR does not include a test. [1] https://github.com/crossbeam-rs/crossbeam/blob/crossbeam-channel-0.5.11/crossbeam-channel/src/flavors/list.rs#L625 [2] 2d22628 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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Published in crossbeam-channel 0.5.15. |
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FTR, I'm preparing a RUSTSEC advisory. |
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@taiki-e I mentioned you in the advisory PR because we like to get sign-off from a maintainer before merging an advisory. Not sure if you've seen it? |
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Approved.
By the way, I love this. If NVD CPE team had such a policy, we would not have had problems like github/advisory-database#5064 (comment)... |
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…alfJung,tgross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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…alfJung,tgross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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…alfJung,tgross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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Rollup merge of rust-lang#139553 - petrosagg:channel-double-free, r=RalfJung,tgross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187 Signed-off-by: Petros Angelatos <petrosagg@gmail.com> (cherry picked from commit b9e2ac5)
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This PR is fixing a regression introduced by #121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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…gross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by #121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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…alfJung,tgross35 sync::mpsc: prevent double free on `Drop` This PR is fixing a regression introduced by rust-lang#121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187
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To grab a double-free fix. Link: crossbeam-rs/crossbeam#1187
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This PR is fixing a regression introduced by #121646 that can lead to a double free when dropping the channel. The details of the bug can be found in the corresponding crossbeam PR crossbeam-rs/crossbeam#1187 Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
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Upgrade to avoid the double free on drop Refs: crossbeam-rs/crossbeam#1187
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Upgrade to avoid the double free on drop Refs: crossbeam-rs/crossbeam#1187
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Upgrade to avoid the double free on drop Refs: crossbeam-rs/crossbeam#1187
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Upgrade to avoid the double free on drop Refs: crossbeam-rs/crossbeam#1187
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Summary: update crossbeam-channel to latest (0.5.15) see: crossbeam-rs/crossbeam#1187 Test Plan: cargo generate-lockfile cargo build
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This PR is fixing a regression introduced by #1084 that can lead to a double free when dropping the channel.
The method
Channel::discard_all_messageshas the property that if it observeshead.blockpointing to a non-null pointer it will attempt to free it.The same property holds for the
Channel::dropmethod and so it is critical that wheneverhead.blockis freed it must also be set to a null pointer so that it is freed exactly once.Before #1084 the behavior of
discard_all_messagesensuredhead.blockwasnullafter its execution due to the atomic store right before exiting [1].After #1084
discard_all_messagesatomically swaps the current value ofhead.blockwith a null pointer at the moment the value is read instead of waiting for the end of the function.The problem lies in the fact that
dicard_all_messagescontained two paths that could lead tohead.blockbeing read but only one of them would swap the value. This meant thatdicard_all_messagescould end up observing a non-null block pointer (and therefore attempting to free it) without settinghead.blockto null. This would then lead toChannel::dropmaking a second attempt at dropping the same pointer.The bug is similar to the one previously fixed by #972 and the double free can be reproduced by reverting the reproduction commit from that PR [2].
As with #972 it is quite difficult to trigger this bug without introducing artificial sleeps in critical points so this PR does not include a test.
[1] https://github.com/crossbeam-rs/crossbeam/blob/crossbeam-channel-0.5.11/crossbeam-channel/src/flavors/list.rs#L625
[2] 2d22628