fix(rax_tree): Fix crash caused by element destruction in RaxTreeMap #4228
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fixes dragonflydb#4172 Signed-off-by: Stepan Bagritsevich <[email protected]>
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Can you please explain what the problem is in the PR description? |
kostasrim
reviewed
Nov 29, 2024
| V* ptr = &(*it).second; | ||
| std::allocator_traits<decltype(alloc_)>::destroy(alloc_, ptr); | ||
| alloc_.deallocate(ptr, 1); | ||
| while (true) { |
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There are two things that concern me here:
- Looking at how
raxRecursiveFreeis implemented it callsfree_callback(raxGetData(n)and what I introduced before seems to be on par in that respect becauseV* ptr = &(*it).second;is actually the result ofraxGetData(n). - Since we can reproduce this we should also include an isolated test to assert the root cause of the issue (my mistake not to suggest this earlier)
I would like to understand why deleting the result of raxGetData(n) result in segfault.
P.s. I also checked what Valkey is doing and indeed they use free_callback (they don't iterate like we do) but let's make sure we understand this
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raxFree passes NULL callback to the raxResursiveFree
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So it's not called there
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@BagritsevichStepan do you know how to reproduce this?
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fixes #4172
This is the simplest solution. However, I propose a different solution that will invoke
raxFreeWithCallback. The problem is that this will require a capturing lambda, as we need to passalloc_. Therefore, we need to copy and update theraxFreeWithCallbackmethod for capturing lambdas.Additionally, I believe that the
SeekIteratorshould be removed, as it seems the issue was caused by it