On Tue, Nov 10, 2020 at 1:04 AM Xin Yin <yinxin_1...@aliyun.com> wrote:
>
> For lru_percpu_map update elem, prealloc_lru_pop() may return
> an unclear elem, if the func called by bpf prog and "onallcpus"
> set to false, it may update an elem whith dirty data.
>
> Clear percpu value of the elem, before use it.
>
> Signed-off-by: Xin Yin <yinxin_1...@aliyun.com>
The alternative fix commit d3bec0138bfb ("bpf: Zero-fill re-used
per-cpu map element")
was already merged.
Please double check that it fixes your test.
> ---
> kernel/bpf/hashtab.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 728ffec52cf3..b1f781ec20b6 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -709,6 +709,16 @@ static void pcpu_copy_value(struct bpf_htab *htab, void
> __percpu *pptr,
> }
> }
>
> +static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr)
> +{
> + u32 size = round_up(htab->map.value_size, 8);
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + memset(per_cpu_ptr(pptr, cpu), 0, size);
> + }
> +}
> +
> static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
> {
> return htab->map.map_type == BPF_MAP_TYPE_HASH_OF_MAPS &&
> @@ -1075,6 +1085,9 @@ static int __htab_lru_percpu_map_update_elem(struct
> bpf_map *map, void *key,
> pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
> value, onallcpus);
> } else {
> + if (!onallcpus)
> + pcpu_init_value(htab,
> + htab_elem_get_ptr(l_new, key_size));
> pcpu_copy_value(htab, htab_elem_get_ptr(l_new, key_size),
> value, onallcpus);
> hlist_nulls_add_head_rcu(&l_new->hash_node, head);
> --
> 2.19.5
>
