On Thu, Oct 10, 2024 at 4:25 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > The bpf_get_kmem_cache() is to get a slab cache information from a > virtual address like virt_to_cache(). If the address is a pointer > to a slab object, it'd return a valid kmem_cache pointer, otherwise > NULL is returned. > > It doesn't grab a reference count of the kmem_cache so the caller is > responsible to manage the access. The returned point is marked as > PTR_UNTRUSTED. And the kfunc has KF_RCU_PROTECTED as the slab object > might be protected by RCU. ... > +BTF_ID_FLAGS(func, bpf_get_kmem_cache, KF_RCU_PROTECTED) This flag is unnecessary. PTR_UNTRUSTED can point to absolutely any memory. In this case it likely points to a valid kmem_cache, but the verifier will guard all accesses with probe_read anyway. I can remove this flag while applying.
