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 <ka...@fb.com>
