kcm: Use splice_eof() to flush

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: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index ba22af1..7dee744 100644 (file)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -968,6 +968,19 @@ out_error:
        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_lockless(&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,
 };