Fix a potential use-after-free in DiffNotifyCallback #579

2020-05-08T23:39:57-05:00

lhchavez commented

2020-05-08 23:39:57 -05:00

(Migrated from github.com)

This change makes the DiffNotifyCallback always use an "unowned"
*git.Diff that does not run the finalizer. Since the underlying
git_diff object is still owned by libgit2, we shouldn't be calling
Diff.Free() on it, even by accident, since that would cause a whole lot
of undefined behavior.

Now instead of storing a reference to a *git.Diff in the intermediate
state while the diff operation is being done, create a brand new
*git.Diff for every callback invocation, and only create a fully-owned
*git.Diff when the diff operation is done and the ownership is
transfered to Go.

This change makes the DiffNotifyCallback always use an "unowned" *git.Diff that does _not_ run the finalizer. Since the underlying git_diff object is still owned by libgit2, we shouldn't be calling Diff.Free() on it, even by accident, since that would cause a whole lot of undefined behavior. Now instead of storing a reference to a *git.Diff in the intermediate state while the diff operation is being done, create a brand new *git.Diff for every callback invocation, and only create a fully-owned *git.Diff when the diff operation is done and the ownership is transfered to Go.

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