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 <eric.dumazet@gmail.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
index 9f8463a..47147c9 100644
--- a/kernel/bpf/xskmap.c
+++ b/kernel/bpf/xskmap.c
@@ -192,11 +192,8 @@
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 @@
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 4e937cd7..6615040 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -744,6 +744,8 @@
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);
