linux-kernel - [PATCH bpf] xsk: skip polling event check for unbound socket

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Date:   Fri, 1 Dec 2023 15:10:52 +0900
From:   Yewon Choi <woni9911@...il.com>
To:     Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     threeearcat@...il.com
Subject: [PATCH bpf] xsk: skip polling event check for unbound socket

In xsk_poll(), checking available events and setting mask bits should
be executed only when a socket has been bound. Setting mask bits for
unbound socket is meaningless.
Currently, it checks events even when xsk_check_common() failed.
To prevent this, we move goto location (skip_tx) after that checking.

Fixes: 1596dae2f17e ("xsk: check IFF_UP earlier in Tx path")
Signed-off-by: Yewon Choi <woni9911@...il.com>
---
 net/xdp/xsk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index ae9f8cb611f6..1e5a65326d1d 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -947,7 +947,7 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock,
 
 	rcu_read_lock();
 	if (xsk_check_common(xs))
-		goto skip_tx;
+		goto out;
 
 	pool = xs->pool;
 
@@ -959,12 +959,12 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock,
 			xsk_generic_xmit(sk);
 	}
 
-skip_tx:
 	if (xs->rx && !xskq_prod_is_empty(xs->rx))
 		mask |= EPOLLIN | EPOLLRDNORM;
 	if (xs->tx && xsk_tx_writeable(xs))
 		mask |= EPOLLOUT | EPOLLWRNORM;
 
+out:
 	rcu_read_unlock();
 	return mask;
 }
-- 
2.37.3