[PATCH net-next v5 09/14] kcm: Use splice_eof() to flush

David Howells
2023-06-07T14:54:04Z

Allow splice to undo the effects of MSG_MORE after prematurely ending a
splice/sendfile due to getting an EOF condition (->splice_read() returned
0) after splice had called sendmsg() with MSG_MORE set when the user didn't
set MSG_MORE.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Tom Herbert <tom@herbertland.com>
cc: Tom Herbert <tom@quantonium.net>
cc: Cong Wang <cong.wang@bytedance.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: netdev@vger.kernel.org
---
net/kcm/kcmsock.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index ba22af16b96d..d0d8c54562d6 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -968,6 +968,19 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
return err;
}

+static void kcm_splice_eof(struct socket *sock)
+{
+ struct sock *sk = sock->sk;
+ struct kcm_sock *kcm = kcm_sk(sk);
+
+ if (skb_queue_empty(&sk->sk_write_queue))
+ return;
+
+ lock_sock(sk);
+ kcm_write_msgs(kcm);
+ release_sock(sk);
+}
+
static ssize_t kcm_sendpage(struct socket *sock, struct page *page,
int offset, size_t size, int flags)

@@ -1773,6 +1786,7 @@ static const struct proto_ops kcm_dgram_ops = {
.sendmsg = kcm_sendmsg,
.recvmsg = kcm_recvmsg,
.mmap = sock_no_mmap,
+ .splice_eof = kcm_splice_eof,
.sendpage = kcm_sendpage,
};

@@ -1794,6 +1808,7 @@ static const struct proto_ops kcm_seqpacket_ops = {
.sendmsg = kcm_sendmsg,
.recvmsg = kcm_recvmsg,
.mmap = sock_no_mmap,
+ .splice_eof = kcm_splice_eof,
.sendpage = kcm_sendpage,
.splice_read = kcm_splice_read,
};