On Thu, 09 Jul 2020 06:11:04 +0000
Martin KaFai Lau <ka...@fb.com> wrote:
> It makes little sense for copying sk_user_data of reuseport_array during
> sk_clone_lock(). This patch reuses the SK_USER_DATA_NOCOPY bit introduced in
> commit f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if
> tagged").
> It is used to mark the sk_user_data is not supposed to be copied to its clone.
>
> Although the cloned sk's sk_user_data will not be used/freed in
> bpf_sk_reuseport_detach(), this change can still allow the cloned
> sk's sk_user_data to be used by some other means.
>
> Freeing the reuseport_array's sk_user_data does not require a rcu grace
> period. Thus, the existing rcu_assign_sk_user_data_nocopy() is not
> used.
>
> Fixes: 5dc4c4b7d4e8 ("bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY")
> Signed-off-by: Martin KaFai Lau <ka...@fb.com>
> ---
> kernel/bpf/reuseport_array.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c
> index 21cde24386db..a95bc8d7e812 100644
> --- a/kernel/bpf/reuseport_array.c
> +++ b/kernel/bpf/reuseport_array.c
> @@ -20,11 +20,14 @@ static struct reuseport_array *reuseport_array(struct
> bpf_map *map)
> /* The caller must hold the reuseport_lock */
> void bpf_sk_reuseport_detach(struct sock *sk)
> {
> - struct sock __rcu **socks;
> + uintptr_t sk_user_data;
>
> write_lock_bh(&sk->sk_callback_lock);
> - socks = sk->sk_user_data;
> - if (socks) {
> + sk_user_data = (uintptr_t)sk->sk_user_data;
> + if (sk_user_data) {
> + struct sock __rcu **socks;
> +
> + socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
> WRITE_ONCE(sk->sk_user_data, NULL);
> /*
> * Do not move this NULL assignment outside of
> @@ -252,6 +255,7 @@ int bpf_fd_reuseport_array_update_elem(struct bpf_map
> *map, void *key,
> struct sock *free_osk = NULL, *osk, *nsk;
> struct sock_reuseport *reuse;
> u32 index = *(u32 *)key;
> + uintptr_t sk_user_data;
> struct socket *socket;
> int err, fd;
>
> @@ -305,7 +309,8 @@ int bpf_fd_reuseport_array_update_elem(struct bpf_map
> *map, void *key,
> if (err)
> goto put_file_unlock;
>
> - WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
> + sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY;
> + WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
> rcu_assign_pointer(array->ptrs[index], nsk);
> free_osk = osk;
> err = 0;
Thanks for fixing this before I got around to it.
Now we can use reuseport with sockmap splicing :-)
Reviewed-by: Jakub Sitnicki <ja...@cloudflare.com>
