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[PATCH] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock

Juergen Gross posted 1 patch 1 year ago
There is a newer version of this series
drivers/xen/pvcalls-front.c | 46 ++++++++++++++++++++++---------------
1 file changed, 27 insertions(+), 19 deletions(-)
[PATCH] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock
Posted by Juergen Gross 1 year ago 
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@gmail.com>
Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/xen/pvcalls-front.c | 46 ++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index d5d589bda243..6e5d712e3115 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -227,22 +227,31 @@ 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 +442,18 @@ 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 +829,28 @@ 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) {
+		free_active_ring(map2);
+		kfree(map2);
 		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 			  (void *)&map->passive.flags);
 		spin_unlock(&bedata->socket_lock);
-		free_active_ring(map2);
-		kfree(map2);
 		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
Re: [PATCH] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock
Posted by Oleksandr Tyshchenko 1 year ago 

On 28.03.23 12:39, Juergen Gross wrote:

Hello Juergen


> 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@gmail.com>
> Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>   drivers/xen/pvcalls-front.c | 46 ++++++++++++++++++++++---------------
>   1 file changed, 27 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index d5d589bda243..6e5d712e3115 100644
> --- a/drivers/xen/pvcalls-front.c
> +++ b/drivers/xen/pvcalls-front.c
> @@ -227,22 +227,31 @@ 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 +442,18 @@ 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 +829,28 @@ 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) {
> +		free_active_ring(map2);
> +		kfree(map2);
>   		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
>   			  (void *)&map->passive.flags);
>   		spin_unlock(&bedata->socket_lock);


Looks like we also need to remove spin_unlock() above, correct?


> -		free_active_ring(map2);
> -		kfree(map2);
>   		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);
Re: [PATCH] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock
Posted by Juergen Gross 1 year ago 
On 28.03.23 12:34, Oleksandr Tyshchenko wrote:
> 
> 
> On 28.03.23 12:39, Juergen Gross wrote:
> 
> Hello Juergen
> 
> 
>> 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@gmail.com>
>> Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>   drivers/xen/pvcalls-front.c | 46 ++++++++++++++++++++++---------------
>>   1 file changed, 27 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
>> index d5d589bda243..6e5d712e3115 100644
>> --- a/drivers/xen/pvcalls-front.c
>> +++ b/drivers/xen/pvcalls-front.c
>> @@ -227,22 +227,31 @@ 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 +442,18 @@ 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 +829,28 @@ 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) {
>> +        free_active_ring(map2);
>> +        kfree(map2);
>>           clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
>>                 (void *)&map->passive.flags);
>>           spin_unlock(&bedata->socket_lock);
> 
> 
> Looks like we also need to remove spin_unlock() above, correct?

Thanks for catching!


Juergen

Patchew 2.1-devel-0870f84

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