On Tue, 8 Sep 2026, Petr Mladek wrote: > When a module is loaded, klp_module_coming() updates all enabled > livepatches. If an error occurs, it delegates cleanup to > klp_cleanup_module_patches_limited(). However, this cleanup loop skips > the partially updated patch, leaving any changes made prior to failure > unreverted. > > One unhandled failure path occurs inside klp_apply_object_relocs(). On > architectures like x86_64, apply_relocate_add() performs a verification > step using memcmp() to check that memory contains the expected relocated > or zeroed value. If relocations left behind by a failed patch are not > cleared, subsequent patch operations or reloads can fail this validation. > > Introduce klp_write_object_relocs_limited() to unwind and clear only the > relocations that were successfully applied before klp_write_object_relocs() > encountered an error. > > There is no need to clear relocations for other objects in the failing > patch because klp_module_coming() operates strictly on the specific > module being loaded.
Hm, I spent some quite time on that and I am not sure if I deciphered everything correctly. It seems to me that all error handling in those paths you are mentioning above is correct and the only problematic thing is that klp_apply_object_relocs() in klp_init_object_loaded() returns ret immediately which leaves partially applied relocations in case of an error. Following calls in klp_init_object_loaded() go through err: label where klp_free_object_loaded() is called which should be fine. Is it correct? Wouldn't be better to be somehow consistent and clean up right in the error path of klp_apply_object_relocs() call in klp_init_object_loaded() similarly to what is already there. After all we want to clean the object. But I also see why you want to do it this way. It only seems more fragile to me. Miroslav
