Patch "skmsg: Schedule psock work if the cached skb exists on the psock" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    skmsg: Schedule psock work if the cached skb exists on the psock

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     skmsg-schedule-psock-work-if-the-cached-skb-exists-o.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e8f19298f3c4ce670bff64f3811caeaf5f11b6b1
Author: Liu Jian <liujian56@xxxxxxxxxx>
Date:   Wed Sep 7 15:13:11 2022 +0800

    skmsg: Schedule psock work if the cached skb exists on the psock
    
    [ Upstream commit bec217197b412d74168c6a42fc0f76d0cc9cad00 ]
    
    In sk_psock_backlog function, for ingress direction skb, if no new data
    packet arrives after the skb is cached, the cached skb does not have a
    chance to be added to the receive queue of psock. As a result, the cached
    skb cannot be received by the upper-layer application. Fix this by reschedule
    the psock work to dispose the cached skb in sk_msg_recvmsg function.
    
    Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
    Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20220907071311.60534-1-liujian56@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 054073c7cbb9..736d8b035a67 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -435,8 +435,10 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 			if (copied + copy > len)
 				copy = len - copied;
 			copy = copy_page_to_iter(page, sge->offset, copy, iter);
-			if (!copy)
-				return copied ? copied : -EFAULT;
+			if (!copy) {
+				copied = copied ? copied : -EFAULT;
+				goto out;
+			}
 
 			copied += copy;
 			if (likely(!peek)) {
@@ -456,7 +458,7 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 				 * didn't copy the entire length lets just break.
 				 */
 				if (copy != sge->length)
-					return copied;
+					goto out;
 				sk_msg_iter_var_next(i);
 			}
 
@@ -478,7 +480,9 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 		}
 		msg_rx = sk_psock_peek_msg(psock);
 	}
-
+out:
+	if (psock->work_state.skb && copied > 0)
+		schedule_work(&psock->work);
 	return copied;
 }
 EXPORT_SYMBOL_GPL(sk_msg_recvmsg);