From f3dda7a679df183e798b86e7b6ec05ab35476de3 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 8 Jul 2020 23:11:04 -0700 Subject: [PATCH] bpf: net: Avoid copying sk_user_data of reuseport_array during sk_clone 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 Signed-off-by: Daniel Borkmann Reviewed-by: Jakub Sitnicki Link: https://lore.kernel.org/bpf/20200709061104.4018798-1-kafai@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; -- 2.39.5