linux-kernel - [PATCH v2] xen/pvcalls: don't call bind_evtchn_to

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Date:   Mon,  3 Apr 2023 11:27:11 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        xen-devel@...ts.xenproject.org, Dan Carpenter <error27@...il.com>
Subject: [PATCH v2] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock

bind_evtchn_to_irqhandler() shouldn't be called under spinlock, as it
can sleep.

This requires to move the calls of create_active() out of the locked
regions. This is no problem, as the worst which could happen would be
a spurious call of the interrupt handler, causing a spurious wake_up().

Reported-by: Dan Carpenter <error27@...il.com>
Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
Signed-off-by: Juergen Gross <jgross@...e.com>
---
V2:
- remove stale spin_unlock() (Oleksandr Tyshchenko)
---
 drivers/xen/pvcalls-front.c | 46 +++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index d5d589bda243..b72ee9379d77 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -227,22 +227,30 @@ static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 
 static void free_active_ring(struct sock_mapping *map);
 
-static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
-				   struct sock_mapping *map)
+static void pvcalls_front_destroy_active(struct pvcalls_bedata *bedata,
+					 struct sock_mapping *map)
 {
 	int i;
 
 	unbind_from_irqhandler(map->active.irq, map);
 
-	spin_lock(&bedata->socket_lock);
-	if (!list_empty(&map->list))
-		list_del_init(&map->list);
-	spin_unlock(&bedata->socket_lock);
+	if (bedata) {
+		spin_lock(&bedata->socket_lock);
+		if (!list_empty(&map->list))
+			list_del_init(&map->list);
+		spin_unlock(&bedata->socket_lock);
+	}
 
 	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 		gnttab_end_foreign_access(map->active.ring->ref[i], NULL);
 	gnttab_end_foreign_access(map->active.ref, NULL);
 	free_active_ring(map);
+}
+
+static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
+				   struct sock_mapping *map)
+{
+	pvcalls_front_destroy_active(bedata, map);
 
 	kfree(map);
 }
@@ -433,19 +441,18 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
-
-	spin_lock(&bedata->socket_lock);
-	ret = get_request(bedata, &req_id);
+	ret = create_active(map, &evtchn);
 	if (ret < 0) {
-		spin_unlock(&bedata->socket_lock);
 		free_active_ring(map);
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
-	ret = create_active(map, &evtchn);
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
 	if (ret < 0) {
 		spin_unlock(&bedata->socket_lock);
-		free_active_ring(map);
+		pvcalls_front_destroy_active(NULL, map);
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
@@ -821,28 +828,27 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
-	spin_lock(&bedata->socket_lock);
-	ret = get_request(bedata, &req_id);
+	ret = create_active(map2, &evtchn);
 	if (ret < 0) {
-		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
-			  (void *)&map->passive.flags);
-		spin_unlock(&bedata->socket_lock);
 		free_active_ring(map2);
 		kfree(map2);
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
 
-	ret = create_active(map2, &evtchn);
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
 	if (ret < 0) {
-		free_active_ring(map2);
-		kfree(map2);
 		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 			  (void *)&map->passive.flags);
 		spin_unlock(&bedata->socket_lock);
+		pvcalls_front_free_map(bedata, map2);
 		pvcalls_exit_sock(sock);
 		return ret;
 	}
+
 	list_add_tail(&map2->list, &bedata->socket_mappings);
 
 	req = RING_GET_REQUEST(&bedata->ring, req_id);
-- 
2.35.3