fix: enforce write permission check on path-based truncate#402
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Path-based truncate() bypassed write permission checks when set_user() was active. POSIX truncate(2) requires write permission on the file, but only the filehandle form was checking (via the handle's write flag). Add _check_perms($mock, 2) for path-based calls when $_mock_uid is set, returning EACCES on denial. Root (uid 0) bypasses as expected. Closes cpan-authors#354 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This was referenced May 18, 2026
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What
Add write permission check for path-based
truncate()whenset_user()is active.Why
POSIX
truncate(2)requires write permission on the file. The filehandle form already checked via the handle's write flag, but path-based truncate skipped permission checks entirely — allowingtruncate('/readonly-file', 0)to succeed underset_user().How
Call
_check_perms($mock, 2)for path-based calls (non-ref$file_or_fh) when$_mock_uidis defined. Returns EACCES on denial; root bypasses as expected.Testing
Three new subtests in
t/truncate.t:Full test suite passes.
Closes #354
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