The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 144748eb0c445091466c9b741ebd0bfcc5914f3d Mon Sep 17 00:00:00 2001
From: John Fastabend john.fastabend@gmail.com Date: Thu, 1 Apr 2021 15:00:40 -0700 Subject: [PATCH] bpf, sockmap: Fix incorrect fwd_alloc accounting
Incorrect accounting fwd_alloc can result in a warning when the socket is torn down,
[18455.319240] WARNING: CPU: 0 PID: 24075 at net/core/stream.c:208 sk_stream_kill_queues+0x21f/0x230 [...] [18455.319543] Call Trace: [18455.319556] inet_csk_destroy_sock+0xba/0x1f0 [18455.319577] tcp_rcv_state_process+0x1b4e/0x2380 [18455.319593] ? lock_downgrade+0x3a0/0x3a0 [18455.319617] ? tcp_finish_connect+0x1e0/0x1e0 [18455.319631] ? sk_reset_timer+0x15/0x70 [18455.319646] ? tcp_schedule_loss_probe+0x1b2/0x240 [18455.319663] ? lock_release+0xb2/0x3f0 [18455.319676] ? __release_sock+0x8a/0x1b0 [18455.319690] ? lock_downgrade+0x3a0/0x3a0 [18455.319704] ? lock_release+0x3f0/0x3f0 [18455.319717] ? __tcp_close+0x2c6/0x790 [18455.319736] ? tcp_v4_do_rcv+0x168/0x370 [18455.319750] tcp_v4_do_rcv+0x168/0x370 [18455.319767] __release_sock+0xbc/0x1b0 [18455.319785] __tcp_close+0x2ee/0x790 [18455.319805] tcp_close+0x20/0x80
This currently happens because on redirect case we do skb_set_owner_r() with the original sock. This increments the fwd_alloc memory accounting on the original sock. Then on redirect we may push this into the queue of the psock we are redirecting to. When the skb is flushed from the queue we give the memory back to the original sock. The problem is if the original sock is destroyed/closed with skbs on another psocks queue then the original sock will not have a way to reclaim the memory before being destroyed. Then above warning will be thrown
sockA sockB
sk_psock_strp_read() sk_psock_verdict_apply() -- SK_REDIRECT -- sk_psock_skb_redirect() skb_queue_tail(psock_other->ingress_skb..)
sk_close() sock_map_unref() sk_psock_put() sk_psock_drop() sk_psock_zap_ingress()
At this point we have torn down our own psock, but have the outstanding skb in psock_other. Note that SK_PASS doesn't have this problem because the sk_psock_drop() logic releases the skb, its still associated with our psock.
To resolve lets only account for sockets on the ingress queue that are still associated with the current socket. On the redirect case we will check memory limits per 6fa9201a89898, but will omit fwd_alloc accounting until skb is actually enqueued. When the skb is sent via skb_send_sock_locked or received with sk_psock_skb_ingress memory will be claimed on psock_other.
Fixes: 6fa9201a89898 ("bpf, sockmap: Avoid returning unneeded EAGAIN when redirecting to self") Reported-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: John Fastabend john.fastabend@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/161731444013.68884.4021114312848535993.stgit@joh...
diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 1261512d6807..5def3a2e85be 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -488,6 +488,7 @@ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb if (unlikely(!msg)) return -EAGAIN; sk_msg_init(msg); + skb_set_owner_r(skb, sk); return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg); }
@@ -790,7 +791,6 @@ static void sk_psock_tls_verdict_apply(struct sk_buff *skb, struct sock *sk, int { switch (verdict) { case __SK_REDIRECT: - skb_set_owner_r(skb, sk); sk_psock_skb_redirect(skb); break; case __SK_PASS: @@ -808,10 +808,6 @@ int sk_psock_tls_strp_read(struct sk_psock *psock, struct sk_buff *skb) rcu_read_lock(); prog = READ_ONCE(psock->progs.skb_verdict); if (likely(prog)) { - /* We skip full set_owner_r here because if we do a SK_PASS - * or SK_DROP we can skip skb memory accounting and use the - * TLS context. - */ skb->sk = psock->sk; tcp_skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); @@ -880,12 +876,13 @@ static void sk_psock_strp_read(struct strparser *strp, struct sk_buff *skb) kfree_skb(skb); goto out; } - skb_set_owner_r(skb, sk); prog = READ_ONCE(psock->progs.skb_verdict); if (likely(prog)) { + skb->sk = sk; tcp_skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb)); + skb->sk = NULL; } sk_psock_verdict_apply(psock, skb, ret); out: @@ -956,12 +953,13 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb, kfree_skb(skb); goto out; } - skb_set_owner_r(skb, sk); prog = READ_ONCE(psock->progs.skb_verdict); if (likely(prog)) { + skb->sk = sk; tcp_skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb)); + skb->sk = NULL; } sk_psock_verdict_apply(psock, skb, ret); out: