On Wed, Aug 5, 2026 at 7:30 AM Josh Poimboeuf <[email protected]> wrote: > > From: Joe Lawrence <[email protected]> > > klp_reloc_needed() returns true for module exports to support > late-module patching. However, clone_reloc_klp() unconditionally > rejects symbols without a twin (i.e., new references added by the > patch), even when the symbol is a known export from Module.symvers. > > Relax the check: allow new references to exported symbols by only > erroring on !twin when there is no export. The export metadata from > Module.symvers provides sufficient context to emit the klp-relocation > without a twin. > > For a module export that isn't sufficient on its own though, as the > resulting klp relocation will only be resolved at patch-enable time if > the exporting module is loaded. > > If the original (unpatched) module already depends on the exporting > module, the dependency is safe: the module loader ensures the dependency > is satisfied before the patched module can be loaded, so the > klp relocation target will exist. > > However, if the patch introduces a reference to a module that the > original doesn't depend on, there is no such guarantee. The exporting > module could be absent or could be unloaded at any time, leading to a > relocation failure or use-after-free. > > So also add a build-time check: when a new symbol reference (no twin) > targets a module export, verify that the original module already has at > least one UNDEF symbol resolving to that same exporting module. If not, > error out with a diagnostic message. > > Signed-off-by: Joe Lawrence <[email protected]> > Signed-off-by: Josh Poimboeuf <[email protected]>
Acked-by: Song Liu <[email protected]>
