dns: refactor QueryWrap lifetime management - #26253
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- Prefer RAII-style management over manual resource management. - Prefer `env->SetImmediate()` over a separate `uv_async_t`. - Perform `ares_destroy()` before possibly tearing down c-ares state. - Verify that the number of active queries is non-negative. - Let pending callbacks know when their underlying `QueryWrap` object has been destroyed. The last item has been a real bug, in that when Workers shut down during currently running DNS queries, they may run into use-after-free situations because: 1. Shutting the `Worker` down leads to the cleanup code deleting the `QueryWrap` objects first; then 2. deleting the `ChannelWrap` object (as it has been created before the `QueryWrap`s), whose destructor runs `ares_destroy()`, which in turn invokes all pending query callbacks with `ARES_ECANCELLED`, 3. which lead to use-after-free, as the callback tried to access the deleted `QueryWrap` object. The added test verifies that this is no longer an issue.
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@addaleax build started: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/2700/pipeline |
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Maybe one of @XadillaX @gireeshpunathil @joyeecheung @cjihrig could review this? |
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cjihrig
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jasnell
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- Prefer RAII-style management over manual resource management. - Prefer `env->SetImmediate()` over a separate `uv_async_t`. - Perform `ares_destroy()` before possibly tearing down c-ares state. - Verify that the number of active queries is non-negative. - Let pending callbacks know when their underlying `QueryWrap` object has been destroyed. The last item has been a real bug, in that when Workers shut down during currently running DNS queries, they may run into use-after-free situations because: 1. Shutting the `Worker` down leads to the cleanup code deleting the `QueryWrap` objects first; then 2. deleting the `ChannelWrap` object (as it has been created before the `QueryWrap`s), whose destructor runs `ares_destroy()`, which in turn invokes all pending query callbacks with `ARES_ECANCELLED`, 3. which lead to use-after-free, as the callback tried to access the deleted `QueryWrap` object. The added test verifies that this is no longer an issue. PR-URL: #26253 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
addaleax
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- Prefer RAII-style management over manual resource management. - Prefer `env->SetImmediate()` over a separate `uv_async_t`. - Perform `ares_destroy()` before possibly tearing down c-ares state. - Verify that the number of active queries is non-negative. - Let pending callbacks know when their underlying `QueryWrap` object has been destroyed. The last item has been a real bug, in that when Workers shut down during currently running DNS queries, they may run into use-after-free situations because: 1. Shutting the `Worker` down leads to the cleanup code deleting the `QueryWrap` objects first; then 2. deleting the `ChannelWrap` object (as it has been created before the `QueryWrap`s), whose destructor runs `ares_destroy()`, which in turn invokes all pending query callbacks with `ARES_ECANCELLED`, 3. which lead to use-after-free, as the callback tried to access the deleted `QueryWrap` object. The added test verifies that this is no longer an issue. PR-URL: #26253 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
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has been destroyed.
The last item has been a real bug, in that when Workers shut down
during currently running DNS queries, they may run into use-after-free
situations because:
the QueryWrap objects first; then
the QueryWraps), whose destructor runs ares_destroy(), which
in turn invokes all pending query callbacks with ARES_ECANCELLED,
deleted QueryWrap object.
The added test verifies that this is no longer an issue.
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