From: Björn Töpel Date: Mon, 8 Oct 2018 17:40:16 +0000 (+0200) Subject: xsk: do not call synchronize_net() under RCU read lock X-Git-Tag: v4.19~18^2~39^2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=cee271678d0e3177a25d0fcb2fa5e051d48e4262;p=linux.git xsk: do not call synchronize_net() under RCU read lock The XSKMAP update and delete functions called synchronize_net(), which can sleep. It is not allowed to sleep during an RCU read section. Instead we need to make sure that the sock sk_destruct (xsk_destruct) function is asynchronously called after an RCU grace period. Setting the SOCK_RCU_FREE flag for XDP sockets takes care of this. Fixes: fbfc504a24f5 ("bpf: introduce new bpf AF_XDP map type BPF_MAP_TYPE_XSKMAP") Reported-by: Eric Dumazet Signed-off-by: Björn Töpel Acked-by: Song Liu Signed-off-by: Daniel Borkmann --- diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c index 9f8463afda9c..47147c9e184d 100644 --- a/kernel/bpf/xskmap.c +++ b/kernel/bpf/xskmap.c @@ -192,11 +192,8 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value, sock_hold(sock->sk); old_xs = xchg(&m->xsk_map[i], xs); - if (old_xs) { - /* Make sure we've flushed everything. */ - synchronize_net(); + if (old_xs) sock_put((struct sock *)old_xs); - } sockfd_put(sock); return 0; @@ -212,11 +209,8 @@ static int xsk_map_delete_elem(struct bpf_map *map, void *key) return -EINVAL; old_xs = xchg(&m->xsk_map[k], NULL); - if (old_xs) { - /* Make sure we've flushed everything. */ - synchronize_net(); + if (old_xs) sock_put((struct sock *)old_xs); - } return 0; } diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 4e937cd7c17d..661504042d30 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -744,6 +744,8 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol, sk->sk_destruct = xsk_destruct; sk_refcnt_debug_inc(sk); + sock_set_flag(sk, SOCK_RCU_FREE); + xs = xdp_sk(sk); mutex_init(&xs->mutex); spin_lock_init(&xs->tx_completion_lock);