From 4903ee3f9581b92c094ea699cd1a9d828fe1f837 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Wed, 14 Jun 2023 16:16:04 +0000
Subject: [PATCH] Revert "bpf, sockmap: Improved check for empty queue"

This reverts commit ba4fec5bd6f8d802c1b8f87340c26ed42dda3ed4.

It breaks the Android KABI and will be brought back at a later time when
it is safe to do so.

Bug: 161946584
Change-Id: I95c2e59a4854c4e178d11b890e8401bc3cb64b68
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
---
 include/linux/skmsg.h |  1 +
 net/core/skmsg.c      | 32 ++++++++++++++++++++++++--------
 2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 054d7911bfc9..904ff9a32ad6 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -71,6 +71,7 @@ struct sk_psock_link {
 };
 
 struct sk_psock_work_state {
+	struct sk_buff			*skb;
 	u32				len;
 	u32				off;
 };
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index d3ffca1b9646..2dfb6e31e8d0 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -621,12 +621,16 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
 
 static void sk_psock_skb_state(struct sk_psock *psock,
 			       struct sk_psock_work_state *state,
+			       struct sk_buff *skb,
 			       int len, int off)
 {
 	spin_lock_bh(&psock->ingress_lock);
 	if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)) {
+		state->skb = skb;
 		state->len = len;
 		state->off = off;
+	} else {
+		sock_drop(psock->sk, skb);
 	}
 	spin_unlock_bh(&psock->ingress_lock);
 }
@@ -637,17 +641,23 @@ static void sk_psock_backlog(struct work_struct *work)
 	struct sk_psock *psock = container_of(dwork, struct sk_psock, work);
 	struct sk_psock_work_state *state = &psock->work_state;
 	struct sk_buff *skb = NULL;
-	u32 len = 0, off = 0;
 	bool ingress;
+	u32 len, off;
 	int ret;
 
 	mutex_lock(&psock->work_mutex);
-	if (unlikely(state->len)) {
+	if (unlikely(state->skb)) {
+		spin_lock_bh(&psock->ingress_lock);
+		skb = state->skb;
 		len = state->len;
 		off = state->off;
+		state->skb = NULL;
+		spin_unlock_bh(&psock->ingress_lock);
 	}
+	if (skb)
+		goto start;
 
-	while ((skb = skb_peek(&psock->ingress_skb))) {
+	while ((skb = skb_dequeue(&psock->ingress_skb))) {
 		len = skb->len;
 		off = 0;
 		if (skb_bpf_strparser(skb)) {
@@ -656,6 +666,7 @@ static void sk_psock_backlog(struct work_struct *work)
 			off = stm->offset;
 			len = stm->full_len;
 		}
+start:
 		ingress = skb_bpf_ingress(skb);
 		skb_bpf_redirect_clear(skb);
 		do {
@@ -665,7 +676,8 @@ static void sk_psock_backlog(struct work_struct *work)
 							  len, ingress);
 			if (ret <= 0) {
 				if (ret == -EAGAIN) {
-					sk_psock_skb_state(psock, state, len, off);
+					sk_psock_skb_state(psock, state, skb,
+							   len, off);
 
 					/* Delay slightly to prioritize any
 					 * other work that might be here.
@@ -677,16 +689,15 @@ static void sk_psock_backlog(struct work_struct *work)
 				/* Hard errors break pipe and stop xmit. */
 				sk_psock_report_error(psock, ret ? -ret : EPIPE);
 				sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
+				sock_drop(psock->sk, skb);
 				goto end;
 			}
 			off += ret;
 			len -= ret;
 		} while (len);
 
-		skb = skb_dequeue(&psock->ingress_skb);
-		if (!ingress) {
+		if (!ingress)
 			kfree_skb(skb);
-		}
 	}
 end:
 	mutex_unlock(&psock->work_mutex);
@@ -779,6 +790,11 @@ static void __sk_psock_zap_ingress(struct sk_psock *psock)
 		skb_bpf_redirect_clear(skb);
 		sock_drop(psock->sk, skb);
 	}
+	kfree_skb(psock->work_state.skb);
+	/* We null the skb here to ensure that calls to sk_psock_backlog
+	 * do not pick up the free'd skb.
+	 */
+	psock->work_state.skb = NULL;
 	__sk_psock_purge_ingress_msg(psock);
 }
 
@@ -797,6 +813,7 @@ void sk_psock_stop(struct sk_psock *psock)
 	spin_lock_bh(&psock->ingress_lock);
 	sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
 	sk_psock_cork_free(psock);
+	__sk_psock_zap_ingress(psock);
 	spin_unlock_bh(&psock->ingress_lock);
 }
 
@@ -811,7 +828,6 @@ static void sk_psock_destroy(struct work_struct *work)
 	sk_psock_done_strp(psock);
 
 	cancel_delayed_work_sync(&psock->work);
-	__sk_psock_zap_ingress(psock);
 	mutex_destroy(&psock->work_mutex);
 
 	psock_progs_drop(&psock->progs);