Re: [PATCH net] bpf: fix htab map destruction when extra reserve is in use

[David Miller <davem@davemloft.net>]

From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri,  4 Nov 2016 00:01:19 +0100

> Commit a6ed3ea65d98 ("bpf: restore behavior of bpf_map_update_elem")
> added an extra per-cpu reserve to the hash table map to restore old
> behaviour from pre prealloc times. When non-prealloc is in use for a
> map, then problem is that once a hash table extra element has been
> linked into the hash-table, and the hash table is destroyed due to
> refcount dropping to zero, then htab_map_free() -> delete_all_elements()
> will walk the whole hash table and drop all elements via htab_elem_free().
> The problem is that the element from the extra reserve is first fed
> to the wrong backend allocator and eventually freed twice.
> 
> Fixes: a6ed3ea65d98 ("bpf: restore behavior of bpf_map_update_elem")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Acked-by: Alexei Starovoitov <ast@kernel.org>

Applied and queued up for -stable, thanks!