Instead of tracking wmem_queued and sk_mem_charge by incrementing
in the verdict SK_REDIRECT paths and decrementing in the tx work
path use skb_set_owner_w and sock_writeable helpers. This solves
a few issues with the current code. First, in SK_REDIRECT inc on
sk_wmem_queued and sk_mem_charge were being done without the peers
sock lock being held. Under stress this can result in accounting
errors when tx work and/or multiple verdict decisions are working
on the peer psock.
Additionally, this cleans up the code because we can rely on the
default destructor to decrement memory accounting on kfree_skb. Also
this will trigger sk_write_space when space becomes available on
kfree_skb() which wasn't happening before and prevent __sk_free
from being called until all in-flight packets are completed.
Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Signed-off-by: John Fastabend <john.fastab...@gmail.com>
Acked-by: Daniel Borkmann <dan...@iogearbox.net>
---
kernel/bpf/sockmap.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index db0d99d..f6ffde9 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -111,7 +111,7 @@ static int smap_verdict_func(struct smap_psock *psock,
struct sk_buff *skb)
static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb)
{
- struct sock *sock;
+ struct sock *sk;
int rc;
/* Because we use per cpu values to feed input from sock redirect
@@ -123,16 +123,16 @@ static void smap_do_verdict(struct smap_psock *psock,
struct sk_buff *skb)
rc = smap_verdict_func(psock, skb);
switch (rc) {
case SK_REDIRECT:
- sock = do_sk_redirect_map();
+ sk = do_sk_redirect_map();
preempt_enable();
- if (likely(sock)) {
- struct smap_psock *peer = smap_psock_sk(sock);
+ if (likely(sk)) {
+ struct smap_psock *peer = smap_psock_sk(sk);
if (likely(peer &&
test_bit(SMAP_TX_RUNNING, &peer->state) &&
- sk_stream_memory_free(peer->sock))) {
- peer->sock->sk_wmem_queued += skb->truesize;
- sk_mem_charge(peer->sock, skb->truesize);
+ !sock_flag(sk, SOCK_DEAD) &&
+ sock_writeable(sk))) {
+ skb_set_owner_w(skb, sk);
skb_queue_tail(&peer->rxqueue, skb);
schedule_work(&peer->tx_work);
break;
@@ -282,16 +282,12 @@ static void smap_tx_work(struct work_struct *w)
/* Hard errors break pipe and stop xmit */
smap_report_sk_error(psock, n ? -n : EPIPE);
clear_bit(SMAP_TX_RUNNING, &psock->state);
- sk_mem_uncharge(psock->sock, skb->truesize);
- psock->sock->sk_wmem_queued -= skb->truesize;
kfree_skb(skb);
goto out;
}
rem -= n;
off += n;
} while (rem);
- sk_mem_uncharge(psock->sock, skb->truesize);
- psock->sock->sk_wmem_queued -= skb->truesize;
kfree_skb(skb);
}
out:
