RE: [Patch bpf] udp: fix a memory leak in udp_read_sock()
From: John Fastabend <john.fastabend@gmail.com>
Date: 2021-05-18 05:36:40
Also in:
bpf
Cong Wang wrote:
From: Cong Wang <redacted> sk_psock_verdict_recv() clones the skb and uses the clone afterward, so udp_read_sock() should free the original skb after done using it.
The clone only happens if sk_psock_verdict_recv() returns >0.
quoted hunk ↗ jump to hunk
Fixes: d7f571188ecf ("udp: Implement ->read_sock() for sockmap") Cc: John Fastabend <john.fastabend@gmail.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Jakub Sitnicki <jakub@cloudflare.com> Cc: Lorenz Bauer <redacted> Signed-off-by: Cong Wang <redacted> --- net/ipv4/udp.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 15f5504adf5b..e31d67fd5183 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c@@ -1798,11 +1798,13 @@ int udp_read_sock(struct sock *sk, read_descriptor_t *desc, if (used <= 0) { if (!copied) copied = used; + kfree_skb(skb);
This case is different from the TCP side, if there is an error the sockmap side will also call kfree_skb(). In TCP side we peek the skb because we don't want to drop it. On UDP side this will just drop data on the floor. Its not super friendly, but its UDP so we are making the assumption this is ok? We've tried to remove all the drop data cases from TCP it would be nice to not drop data on UDP side if we can help it. Could we requeue or peek the UDP skb to avoid this?
break;
} else if (used <= skb->len) {
copied += used;
}
+ kfree_skb(skb);
if (!desc->count)
break;
}
--
2.25.1