Fix segfault caused double erase from child_pid rb tree #2554
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In a situation when a child was timed out, but not yet processed, the thread is THREAD_CHILD_TIMEOUT type and remains on ready queue. If it gets terminated in this state, it needs to be removed from rb tree child_pid and transitioned to THREAD_CHILD_TERMINATED, but without additional moving it to ready queue as it is already there. The erase from child_pid tree is required to clean up pid from not terminated childs tree, but it needs to be done exactly once as rb tree implementation is not guarded against double removal. Erasing or adding same element multiple times, leads to malformed red-black tree and segmentation faults. This patch removes double erase in described scenario. Signed-off-by: Lukasz Wojciechowski <[email protected]>
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The previous erase was done 9 lines above in line 2204 |
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@lukaszwojciechowski Thank you very much for identifying this issue and providing the patch. |
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In a situation when a child was timed out, but not yet processed, the thread is THREAD_CHILD_TIMEOUT type and remains on ready queue. If it gets terminated in this state, it needs to be removed from rb tree child_pid and transitioned to THREAD_CHILD_TERMINATED, but without additional moving it to ready queue as it is already there.
The erase from child_pid tree is required to clean up pid from not terminated childs tree, but it needs to be done exactly once as rb tree implementation is not guarded against double removal. Erasing or adding same element multiple times, leads to malformed red-black tree and segmentation faults.
This patch removes double erase in described scenario.
Might fix #2548