yq/pkg
Jan Dubois 0374ad6b4b
Fix stack overflow from circular alias in traverse (#2647)
go-yaml accepts cross-document alias references, which the YAML spec
forbids (anchors are scoped to a single document). When a nested
assignment targets such an alias, UpdateFrom copies the Alias field
between nodes, creating a self-referencing AliasNode. Both traverse()
and traverseArrayIndices() then follow this cycle indefinitely.

Extract resolveAliasChain(), which follows aliases iteratively with a
visited set and returns an error on cycles. Both traverse() and
traverseArrayIndices() now call it, eliminating the recursive alias
handling in both code paths.

Note: traverseMergeAnchor() also dereferences aliases (lines 358 and
371) but with single-step assignment, not recursion. A self-referencing
alias there falls through the kind switch silently rather than
crashing. Using resolveAliasChain() in that function would produce a
clear error instead of silently dropping the node.

Reproducer (stack overflow before this fix, returns error after):

    echo '&-- a
    ---
    *--' | yq eval-all '. = (.x = 1)'

Found by OSS-Fuzz via the lima project's FuzzEvaluateExpression target.
https://issues.oss-fuzz.com/issues/390467412

Signed-off-by: Jan Dubois <jan@jandubois.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-06 18:25:13 +10:00
..
yqlib Fix stack overflow from circular alias in traverse (#2647) 2026-04-06 18:25:13 +10:00