From: John Fastabend john.fastabend@gmail.com
[ Upstream commit 9b2e0388bec8ec5427403e23faff3b58dd1c3200 ]
When sockmap code is using the stream parser it also handles the write space events in order to handle the case where (a) verdict redirects skb to another socket and (b) the sockmap then sends the skb but due to memory constraints (or other EAGAIN errors) needs to do a retry.
But the initial code missed a third case where the skb_send_sock_locked() triggers an sk_wait_event(). A typically case would be when sndbuf size is exceeded. If this happens because we do not pass the write_space event to the lower layers we never wake up the event and it will wait for sndtimeo. Which as noted in ktls fix may be rather large and look like a hang to the user.
To reproduce the best test is to reduce the sndbuf size and send 1B data chunks to stress the memory handling. To fix this pass the event from the upper layer to the lower layer.
Signed-off-by: John Fastabend john.fastabend@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- kernel/bpf/sockmap.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c index e7f65afc4e24..ed707b21d152 100644 --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -1430,12 +1430,15 @@ static void smap_tx_work(struct work_struct *w) static void smap_write_space(struct sock *sk) { struct smap_psock *psock; + void (*write_space)(struct sock *sk);
rcu_read_lock(); psock = smap_psock_sk(sk); if (likely(psock && test_bit(SMAP_TX_RUNNING, &psock->state))) schedule_work(&psock->tx_work); + write_space = psock->save_write_space; rcu_read_unlock(); + write_space(sk); }
static void smap_stop_sock(struct smap_psock *psock, struct sock *sk)