aug_rm: fix segfault when deleting a tree and one of its ancestors #320
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
Wow that was quick, thanks @lutter ! I was originally drafting the report as a request for help fixing this and in the process identified the root cause of the bug. I've tested the PR and can confirm this fixes the problem I was having. Thanks! |
In a tree like /files/1/2, when we execute 'rm /files//*', the path expression matches /files/1 and /files/1/2. When tree_rm goes to delete these two nodes, it first deletes (frees) /files/1 and all its descendents. By the time we try to delete /files/1/2, the pointer we have to that is no longer valid and we end up causing a double-free. With this change, we make sure we only delete a node if none of its ancestors is being deleted beforehand in the same operation - deleting a node, and one of its ancestors afterwards is fine as the pointer to the ancestor is still valid. Fixes hercules-team#319 Special shoutout to Geoff Williams for finding, diagnosing and filing a great bug report about this.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
In a tree like /files/1/2, when we execute 'rm /files//*', the path
expression matches /files/1 and /files/1/2. When tree_rm goes to delete
these two nodes, it first deletes (frees) /files/1 and all its
descendents. By the time we try to delete /files/1/2, the pointer we have
to that is no longer valid and we end up causing a double-free.
With this change, we make sure we only delete a node if none of its
ancestors is being deleted beforehand in the same operation - deleting a
node, and one of its ancestors afterwards is fine as the pointer to the
ancestor is still valid.
Fixes #319
Special shoutout to Geoff Williams for finding, diagnosing and filing a
great bug report about this.