On Fri, May 1, 2020 at 1:00 PM Martin KaFai Lau <kafai@xxxxxx> wrote: > > On Fri, May 01, 2020 at 11:56:22AM -0700, Andrii Nakryiko wrote: > > If bpf_link_prime() succeeds to allocate new anon file, but then fails to > > allocate ID for it, link priming is considered to be failed and user is > > supposed ot be able to directly kfree() bpf_link, because it was never exposed > > to user-space. > > > > But at that point file already keeps a pointer to bpf_link and will eventually > > call bpf_link_release(), so if bpf_link was kfree()'d by caller, that would > > lead to use-after-free. > > > > Fix this by first allocating ID and only then allocating file. Adding ID to > > link_idr is ok, because link at that point still doesn't have its ID set, so > > no user-space process can create a new FD for it. > Acked-by: Martin KaFai Lau <kafai@xxxxxx> Applied. Thanks
