diff mbox series

[net-next] tun: fix ubuf refcount incorrectly on error path

Message ID 1606982459-41752-1-git-send-email-wangyunjian@huawei.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series [net-next] tun: fix ubuf refcount incorrectly on error path | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net-next
netdev/subject_prefix success Link
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success Link
netdev/stable success Stable not CCed

Commit Message

wangyunjian Dec. 3, 2020, 8 a.m. UTC
From: Yunjian Wang <wangyunjian@huawei.com>

After setting callback for ubuf_info of skb, the callback
(vhost_net_zerocopy_callback) will be called to decrease
the refcount when freeing skb. But when an exception occurs
afterwards, the error handling in vhost handle_tx() will
try to decrease the same refcount again. This is wrong and
fix this by clearing ubuf_info when meeting errors.

Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")

Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
---
 drivers/net/tun.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Comments

Jason Wang Dec. 4, 2020, 6:10 a.m. UTC | #1
On 2020/12/3 下午4:00, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>
>
> After setting callback for ubuf_info of skb, the callback
> (vhost_net_zerocopy_callback) will be called to decrease
> the refcount when freeing skb. But when an exception occurs
> afterwards, the error handling in vhost handle_tx() will
> try to decrease the same refcount again. This is wrong and
> fix this by clearing ubuf_info when meeting errors.
>
> Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
>
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> ---
>   drivers/net/tun.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 2dc1988a8973..3614bb1b6d35 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1861,6 +1861,12 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   	if (unlikely(!(tun->dev->flags & IFF_UP))) {
>   		err = -EIO;
>   		rcu_read_unlock();
> +		if (zerocopy) {
> +			skb_shinfo(skb)->destructor_arg = NULL;
> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> +		}
> +
>   		goto drop;
>   	}
>   
> @@ -1874,6 +1880,11 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   
>   		if (unlikely(headlen > skb_headlen(skb))) {
>   			atomic_long_inc(&tun->dev->rx_dropped);
> +			if (zerocopy) {
> +				skb_shinfo(skb)->destructor_arg = NULL;
> +				skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> +				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> +			}
>   			napi_free_frags(&tfile->napi);
>   			rcu_read_unlock();
>   			mutex_unlock(&tfile->napi_mutex);


It looks to me then we miss the failure feedback.

The issues comes from the inconsistent error handling in tun.

I wonder whether we can simply do uarg->callback(uarg, false) if 
necessary on every failture path on tun_get_user().

Note that, zerocopy has a lot of issues which makes it not good for 
production environment.

Thanks
wangyunjian Dec. 4, 2020, 10:22 a.m. UTC | #2
> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Friday, December 4, 2020 2:11 PM
> To: wangyunjian <wangyunjian@huawei.com>; mst@redhat.com
> Cc: virtualization@lists.linux-foundation.org; netdev@vger.kernel.org; Lilijun
> (Jerry) <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>
> Subject: Re: [PATCH net-next] tun: fix ubuf refcount incorrectly on error path
> 
> 
> On 2020/12/3 下午4:00, wangyunjian wrote:
> > From: Yunjian Wang <wangyunjian@huawei.com>
> >
> > After setting callback for ubuf_info of skb, the callback
> > (vhost_net_zerocopy_callback) will be called to decrease the refcount
> > when freeing skb. But when an exception occurs afterwards, the error
> > handling in vhost handle_tx() will try to decrease the same refcount
> > again. This is wrong and fix this by clearing ubuf_info when meeting
> > errors.
> >
> > Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
> > Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP
> > driver")
> >
> > Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> > ---
> >   drivers/net/tun.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c index
> > 2dc1988a8973..3614bb1b6d35 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -1861,6 +1861,12 @@ static ssize_t tun_get_user(struct tun_struct
> *tun, struct tun_file *tfile,
> >   	if (unlikely(!(tun->dev->flags & IFF_UP))) {
> >   		err = -EIO;
> >   		rcu_read_unlock();
> > +		if (zerocopy) {
> > +			skb_shinfo(skb)->destructor_arg = NULL;
> > +			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> > +			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> > +		}
> > +
> >   		goto drop;
> >   	}
> >
> > @@ -1874,6 +1880,11 @@ static ssize_t tun_get_user(struct tun_struct
> > *tun, struct tun_file *tfile,
> >
> >   		if (unlikely(headlen > skb_headlen(skb))) {
> >   			atomic_long_inc(&tun->dev->rx_dropped);
> > +			if (zerocopy) {
> > +				skb_shinfo(skb)->destructor_arg = NULL;
> > +				skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> > +				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> > +			}
> >   			napi_free_frags(&tfile->napi);
> >   			rcu_read_unlock();
> >   			mutex_unlock(&tfile->napi_mutex);
> 
> 
> It looks to me then we miss the failure feedback.
> 
> The issues comes from the inconsistent error handling in tun.
> 
> I wonder whether we can simply do uarg->callback(uarg, false) if necessary on
> every failture path on tun_get_user().

How about this?

---
 drivers/net/tun.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2dc1988a8973..36a8d8eacd7b 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1637,6 +1637,19 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 	return NULL;
 }
 
+/* copy ubuf_info for callback when skb has no error */
+inline static tun_copy_ubuf_info(struct sk_buff *skb, bool zerocopy, void *msg_control)
+{
+	if (zerocopy) {
+		skb_shinfo(skb)->destructor_arg = msg_control;
+		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+	} else if (msg_control) {
+		struct ubuf_info *uarg = msg_control;
+		uarg->callback(uarg, false);
+	}
+}
+
 /* Get packet from user space buffer */
 static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 			    void *msg_control, struct iov_iter *from,
@@ -1812,16 +1825,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		break;
 	}
 
-	/* copy skb_ubuf_info for callback when skb has no error */
-	if (zerocopy) {
-		skb_shinfo(skb)->destructor_arg = msg_control;
-		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
-		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
-	} else if (msg_control) {
-		struct ubuf_info *uarg = msg_control;
-		uarg->callback(uarg, false);
-	}
-
 	skb_reset_network_header(skb);
 	skb_probe_transport_header(skb);
 	skb_record_rx_queue(skb, tfile->queue_index);
@@ -1830,6 +1833,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		struct bpf_prog *xdp_prog;
 		int ret;
 
+		tun_copy_ubuf_info(skb, zerocopy, msg_control);
 		local_bh_disable();
 		rcu_read_lock();
 		xdp_prog = rcu_dereference(tun->xdp_prog);
@@ -1880,7 +1884,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 			WARN_ON(1);
 			return -ENOMEM;
 		}
-
+		tun_copy_ubuf_info(skb, zerocopy, msg_control);
 		local_bh_disable();
 		napi_gro_frags(&tfile->napi);
 		local_bh_enable();
@@ -1889,6 +1893,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
 		int queue_len;
 
+		tun_copy_ubuf_info(skb, zerocopy, msg_control);
 		spin_lock_bh(&queue->lock);
 		__skb_queue_tail(queue, skb);
 		queue_len = skb_queue_len(queue);
@@ -1899,8 +1904,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
 		local_bh_enable();
 	} else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
+		tun_copy_ubuf_info(skb, zerocopy, msg_control);
 		tun_rx_batched(tun, tfile, skb, more);
 	} else {
+		tun_copy_ubuf_info(skb, zerocopy, msg_control);
 		netif_rx_ni(skb);
 	}
 	rcu_read_unlock();
Jason Wang Dec. 7, 2020, 3:54 a.m. UTC | #3
On 2020/12/4 下午6:22, wangyunjian wrote:
>> -----Original Message-----
>> From: Jason Wang [mailto:jasowang@redhat.com]
>> Sent: Friday, December 4, 2020 2:11 PM
>> To: wangyunjian <wangyunjian@huawei.com>; mst@redhat.com
>> Cc: virtualization@lists.linux-foundation.org; netdev@vger.kernel.org; Lilijun
>> (Jerry) <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>
>> Subject: Re: [PATCH net-next] tun: fix ubuf refcount incorrectly on error path
>>
>>
>> On 2020/12/3 下午4:00, wangyunjian wrote:
>>> From: Yunjian Wang <wangyunjian@huawei.com>
>>>
>>> After setting callback for ubuf_info of skb, the callback
>>> (vhost_net_zerocopy_callback) will be called to decrease the refcount
>>> when freeing skb. But when an exception occurs afterwards, the error
>>> handling in vhost handle_tx() will try to decrease the same refcount
>>> again. This is wrong and fix this by clearing ubuf_info when meeting
>>> errors.
>>>
>>> Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
>>> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP
>>> driver")
>>>
>>> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
>>> ---
>>>    drivers/net/tun.c | 11 +++++++++++
>>>    1 file changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c index
>>> 2dc1988a8973..3614bb1b6d35 100644
>>> --- a/drivers/net/tun.c
>>> +++ b/drivers/net/tun.c
>>> @@ -1861,6 +1861,12 @@ static ssize_t tun_get_user(struct tun_struct
>> *tun, struct tun_file *tfile,
>>>    	if (unlikely(!(tun->dev->flags & IFF_UP))) {
>>>    		err = -EIO;
>>>    		rcu_read_unlock();
>>> +		if (zerocopy) {
>>> +			skb_shinfo(skb)->destructor_arg = NULL;
>>> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
>>> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
>>> +		}
>>> +
>>>    		goto drop;
>>>    	}
>>>
>>> @@ -1874,6 +1880,11 @@ static ssize_t tun_get_user(struct tun_struct
>>> *tun, struct tun_file *tfile,
>>>
>>>    		if (unlikely(headlen > skb_headlen(skb))) {
>>>    			atomic_long_inc(&tun->dev->rx_dropped);
>>> +			if (zerocopy) {
>>> +				skb_shinfo(skb)->destructor_arg = NULL;
>>> +				skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
>>> +				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
>>> +			}
>>>    			napi_free_frags(&tfile->napi);
>>>    			rcu_read_unlock();
>>>    			mutex_unlock(&tfile->napi_mutex);
>>
>> It looks to me then we miss the failure feedback.
>>
>> The issues comes from the inconsistent error handling in tun.
>>
>> I wonder whether we can simply do uarg->callback(uarg, false) if necessary on
>> every failture path on tun_get_user().
> How about this?
>
> ---
>   drivers/net/tun.c | 29 ++++++++++++++++++-----------
>   1 file changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 2dc1988a8973..36a8d8eacd7b 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1637,6 +1637,19 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>   	return NULL;
>   }
>   
> +/* copy ubuf_info for callback when skb has no error */
> +inline static tun_copy_ubuf_info(struct sk_buff *skb, bool zerocopy, void *msg_control)
> +{
> +	if (zerocopy) {
> +		skb_shinfo(skb)->destructor_arg = msg_control;
> +		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> +		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
> +	} else if (msg_control) {
> +		struct ubuf_info *uarg = msg_control;
> +		uarg->callback(uarg, false);
> +	}
> +}
> +
>   /* Get packet from user space buffer */
>   static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   			    void *msg_control, struct iov_iter *from,
> @@ -1812,16 +1825,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   		break;
>   	}
>   
> -	/* copy skb_ubuf_info for callback when skb has no error */
> -	if (zerocopy) {
> -		skb_shinfo(skb)->destructor_arg = msg_control;
> -		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> -		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
> -	} else if (msg_control) {
> -		struct ubuf_info *uarg = msg_control;
> -		uarg->callback(uarg, false);
> -	}
> -
>   	skb_reset_network_header(skb);
>   	skb_probe_transport_header(skb);
>   	skb_record_rx_queue(skb, tfile->queue_index);
> @@ -1830,6 +1833,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   		struct bpf_prog *xdp_prog;
>   		int ret;
>   
> +		tun_copy_ubuf_info(skb, zerocopy, msg_control);


If you think disabling zerocopy for XDP (which I think it makes sense). 
It's better to do this in another patch.


>   		local_bh_disable();
>   		rcu_read_lock();
>   		xdp_prog = rcu_dereference(tun->xdp_prog);
> @@ -1880,7 +1884,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   			WARN_ON(1);
>   			return -ENOMEM;
>   		}
> -
> +		tun_copy_ubuf_info(skb, zerocopy, msg_control);


And for NAPI frags.


>   		local_bh_disable();
>   		napi_gro_frags(&tfile->napi);
>   		local_bh_enable();
> @@ -1889,6 +1893,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   		struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
>   		int queue_len;
>   
> +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
>   		spin_lock_bh(&queue->lock);
>   		__skb_queue_tail(queue, skb);
>   		queue_len = skb_queue_len(queue);
> @@ -1899,8 +1904,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>   
>   		local_bh_enable();
>   	} else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
> +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
>   		tun_rx_batched(tun, tfile, skb, more);
>   	} else {
> +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
>   		netif_rx_ni(skb);
>   	}
>   	rcu_read_unlock();


So it looks to me you want to disable zerocopy in all of the possible 
datapath?

Thanks
wangyunjian Dec. 7, 2020, 1:38 p.m. UTC | #4
> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Monday, December 7, 2020 11:54 AM
> To: wangyunjian <wangyunjian@huawei.com>; mst@redhat.com
> Cc: virtualization@lists.linux-foundation.org; netdev@vger.kernel.org; Lilijun
> (Jerry) <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>
> Subject: Re: [PATCH net-next] tun: fix ubuf refcount incorrectly on error path
> 
> 
> On 2020/12/4 下午6:22, wangyunjian wrote:
> >> -----Original Message-----
> >> From: Jason Wang [mailto:jasowang@redhat.com]
> >> Sent: Friday, December 4, 2020 2:11 PM
> >> To: wangyunjian <wangyunjian@huawei.com>; mst@redhat.com
> >> Cc: virtualization@lists.linux-foundation.org; netdev@vger.kernel.org;
> Lilijun
> >> (Jerry) <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>
> >> Subject: Re: [PATCH net-next] tun: fix ubuf refcount incorrectly on error path
> >>
> >>
> >> On 2020/12/3 下午4:00, wangyunjian wrote:
> >>> From: Yunjian Wang <wangyunjian@huawei.com>
> >>>
> >>> After setting callback for ubuf_info of skb, the callback
> >>> (vhost_net_zerocopy_callback) will be called to decrease the refcount
> >>> when freeing skb. But when an exception occurs afterwards, the error
> >>> handling in vhost handle_tx() will try to decrease the same refcount
> >>> again. This is wrong and fix this by clearing ubuf_info when meeting
> >>> errors.
> >>>
> >>> Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
> >>> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP
> >>> driver")
> >>>
> >>> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> >>> ---
> >>>    drivers/net/tun.c | 11 +++++++++++
> >>>    1 file changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c index
> >>> 2dc1988a8973..3614bb1b6d35 100644
> >>> --- a/drivers/net/tun.c
> >>> +++ b/drivers/net/tun.c
> >>> @@ -1861,6 +1861,12 @@ static ssize_t tun_get_user(struct tun_struct
> >> *tun, struct tun_file *tfile,
> >>>    	if (unlikely(!(tun->dev->flags & IFF_UP))) {
> >>>    		err = -EIO;
> >>>    		rcu_read_unlock();
> >>> +		if (zerocopy) {
> >>> +			skb_shinfo(skb)->destructor_arg = NULL;
> >>> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> >>> +			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> >>> +		}
> >>> +
> >>>    		goto drop;
> >>>    	}
> >>>
> >>> @@ -1874,6 +1880,11 @@ static ssize_t tun_get_user(struct tun_struct
> >>> *tun, struct tun_file *tfile,
> >>>
> >>>    		if (unlikely(headlen > skb_headlen(skb))) {
> >>>    			atomic_long_inc(&tun->dev->rx_dropped);
> >>> +			if (zerocopy) {
> >>> +				skb_shinfo(skb)->destructor_arg = NULL;
> >>> +				skb_shinfo(skb)->tx_flags &=
> ~SKBTX_DEV_ZEROCOPY;
> >>> +				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
> >>> +			}
> >>>    			napi_free_frags(&tfile->napi);
> >>>    			rcu_read_unlock();
> >>>    			mutex_unlock(&tfile->napi_mutex);
> >>
> >> It looks to me then we miss the failure feedback.
> >>
> >> The issues comes from the inconsistent error handling in tun.
> >>
> >> I wonder whether we can simply do uarg->callback(uarg, false) if necessary
> on
> >> every failture path on tun_get_user().
> > How about this?
> >
> > ---
> >   drivers/net/tun.c | 29 ++++++++++++++++++-----------
> >   1 file changed, 18 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 2dc1988a8973..36a8d8eacd7b 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -1637,6 +1637,19 @@ static struct sk_buff *tun_build_skb(struct
> tun_struct *tun,
> >   	return NULL;
> >   }
> >
> > +/* copy ubuf_info for callback when skb has no error */
> > +inline static tun_copy_ubuf_info(struct sk_buff *skb, bool zerocopy, void
> *msg_control)
> > +{
> > +	if (zerocopy) {
> > +		skb_shinfo(skb)->destructor_arg = msg_control;
> > +		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> > +		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
> > +	} else if (msg_control) {
> > +		struct ubuf_info *uarg = msg_control;
> > +		uarg->callback(uarg, false);
> > +	}
> > +}
> > +
> >   /* Get packet from user space buffer */
> >   static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> >   			    void *msg_control, struct iov_iter *from,
> > @@ -1812,16 +1825,6 @@ static ssize_t tun_get_user(struct tun_struct
> *tun, struct tun_file *tfile,
> >   		break;
> >   	}
> >
> > -	/* copy skb_ubuf_info for callback when skb has no error */
> > -	if (zerocopy) {
> > -		skb_shinfo(skb)->destructor_arg = msg_control;
> > -		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> > -		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
> > -	} else if (msg_control) {
> > -		struct ubuf_info *uarg = msg_control;
> > -		uarg->callback(uarg, false);
> > -	}
> > -
> >   	skb_reset_network_header(skb);
> >   	skb_probe_transport_header(skb);
> >   	skb_record_rx_queue(skb, tfile->queue_index);
> > @@ -1830,6 +1833,7 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
> >   		struct bpf_prog *xdp_prog;
> >   		int ret;
> >
> > +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
> 
> 
> If you think disabling zerocopy for XDP (which I think it makes sense).
> It's better to do this in another patch.
> 
> 
> >   		local_bh_disable();
> >   		rcu_read_lock();
> >   		xdp_prog = rcu_dereference(tun->xdp_prog);
> > @@ -1880,7 +1884,7 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
> >   			WARN_ON(1);
> >   			return -ENOMEM;
> >   		}
> > -
> > +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
> 
> 
> And for NAPI frags.
> 
> 
> >   		local_bh_disable();
> >   		napi_gro_frags(&tfile->napi);
> >   		local_bh_enable();
> > @@ -1889,6 +1893,7 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
> >   		struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
> >   		int queue_len;
> >
> > +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
> >   		spin_lock_bh(&queue->lock);
> >   		__skb_queue_tail(queue, skb);
> >   		queue_len = skb_queue_len(queue);
> > @@ -1899,8 +1904,10 @@ static ssize_t tun_get_user(struct tun_struct
> *tun, struct tun_file *tfile,
> >
> >   		local_bh_enable();
> >   	} else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
> > +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
> >   		tun_rx_batched(tun, tfile, skb, more);
> >   	} else {
> > +		tun_copy_ubuf_info(skb, zerocopy, msg_control);
> >   		netif_rx_ni(skb);
> >   	}
> >   	rcu_read_unlock();
> 
> 
> So it looks to me you want to disable zerocopy in all of the possible
> datapath?

I think the newly added code is easy to miss this problem, so I want to
copy ubuf_info until we're sure there's no errors.

Thanks,
Yunjian
> 
> Thanks
Jason Wang Dec. 8, 2020, 2:32 a.m. UTC | #5
On 2020/12/7 下午9:38, wangyunjian wrote:
> I think the newly added code is easy to miss this problem, so I want to
> copy ubuf_info until we're sure there's no errors.
>
> Thanks,
> Yunjian


But isn't this actually a disabling of zerocopy?

Thanks
Jason Wang Dec. 9, 2020, 9:30 a.m. UTC | #6
On 2020/12/8 上午10:32, Jason Wang wrote:
>
> On 2020/12/7 下午9:38, wangyunjian wrote:
>> I think the newly added code is easy to miss this problem, so I want to
>> copy ubuf_info until we're sure there's no errors.
>>
>> Thanks,
>> Yunjian
>
>
> But isn't this actually a disabling of zerocopy?
>
> Thanks
>
>

Sorry, I misread the patch.

Please send a formal version, and let's move the discussion there.

Thanks
diff mbox series

Patch

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2dc1988a8973..3614bb1b6d35 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1861,6 +1861,12 @@  static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	if (unlikely(!(tun->dev->flags & IFF_UP))) {
 		err = -EIO;
 		rcu_read_unlock();
+		if (zerocopy) {
+			skb_shinfo(skb)->destructor_arg = NULL;
+			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
+			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
+		}
+
 		goto drop;
 	}
 
@@ -1874,6 +1880,11 @@  static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
 		if (unlikely(headlen > skb_headlen(skb))) {
 			atomic_long_inc(&tun->dev->rx_dropped);
+			if (zerocopy) {
+				skb_shinfo(skb)->destructor_arg = NULL;
+				skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
+				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
+			}
 			napi_free_frags(&tfile->napi);
 			rcu_read_unlock();
 			mutex_unlock(&tfile->napi_mutex);