Re: RE: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

5 messages, 3 authors, 2021-06-02 · open the first message on its own page

Re: RE: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2021-05-24 02:07:14 

On Mon, 24 May 2021 01:48:53 +0000, Guodeqing (A) [off-list ref] wrote:
quoted
-----Original Message-----
From: Max Gurtovoy [mailto:mgurtovoy@nvidia.com]
Sent: Sunday, May 23, 2021 15:25
To: Guodeqing (A) <redacted>; mst@redhat.com
Cc: jasowang@redhat.com; davem@davemloft.net; kuba@kernel.org;
virtualization@lists.linux-foundation.org; netdev@vger.kernel.org
Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem


On 5/22/2021 11:02 AM, guodeqing wrote:
quoted
If the virtio_net device does not suppurt the ctrl queue feature, the
vi->ctrl was not allocated, so there is no need to free it.
you don't need this check.

from kfree doc:

"If @objp is NULL, no operation is performed."

This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.

  yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe
  be freed which  was not allocated, this may give people a misunderstanding.
  Thanks.

I think it may be enough to add a comment, and the code does not need to be
modified.

Thanks.

quoted
quoted
Here I adjust the initialization sequence and the check of vi->has_cvq
to slove this problem.

Fixes: 	122b84a1267a ("virtio-net: don't allocate control_buf if not
supported")
quoted
Signed-off-by: guodeqing <redacted>
---
  drivers/net/virtio_net.c | 20 ++++++++++----------
  1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index
9b6a4a875c55..894f894d3a29 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2691,7 +2691,8 @@ static void virtnet_free_queues(struct
virtnet_info *vi)

  	kfree(vi->rq);
  	kfree(vi->sq);
-	kfree(vi->ctrl);
+	if (vi->has_cvq)
+		kfree(vi->ctrl);
  }

  static void _free_receive_bufs(struct virtnet_info *vi) @@ -2870,13
+2871,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
  {
  	int i;

-	if (vi->has_cvq) {
-		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
-		if (!vi->ctrl)
-			goto err_ctrl;
-	} else {
-		vi->ctrl = NULL;
-	}
  	vi->sq = kcalloc(vi->max_queue_pairs, sizeof(*vi->sq), GFP_KERNEL);
  	if (!vi->sq)
  		goto err_sq;
@@ -2884,6 +2878,12 @@ static int virtnet_alloc_queues(struct
virtnet_info *vi)
quoted
  	if (!vi->rq)
  		goto err_rq;

+	if (vi->has_cvq) {
+		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
+		if (!vi->ctrl)
+			goto err_ctrl;
+	}
+
  	INIT_DELAYED_WORK(&vi->refill, refill_work);
  	for (i = 0; i < vi->max_queue_pairs; i++) {
  		vi->rq[i].pages = NULL;
@@ -2902,11 +2902,11 @@ static int virtnet_alloc_queues(struct
virtnet_info *vi)

  	return 0;

+err_ctrl:
+	kfree(vi->rq);
  err_rq:
  	kfree(vi->sq);
  err_sq:
-	kfree(vi->ctrl);
-err_ctrl:
  	return -ENOMEM;
  }
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Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

    

      From: Jason Wang <hidden>

      Date: 2021-05-24 02:37:24 
    

  

  
在 2021/5/24 上午10:06, Xuan Zhuo 写道:
On Mon, 24 May 2021 01:48:53 +0000, Guodeqing (A) [off-list ref] wrote:
quoted
quoted
-----Original Message-----
From: Max Gurtovoy [mailto:mgurtovoy@nvidia.com]
Sent: Sunday, May 23, 2021 15:25
To: Guodeqing (A) <redacted>; mst@redhat.com
Cc: jasowang@redhat.com; davem@davemloft.net; kuba@kernel.org;
virtualization@lists.linux-foundation.org; netdev@vger.kernel.org
Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem


On 5/22/2021 11:02 AM, guodeqing wrote:
quoted
If the virtio_net device does not suppurt the ctrl queue feature, the
vi->ctrl was not allocated, so there is no need to free it.
you don't need this check.

from kfree doc:

"If @objp is NULL, no operation is performed."

This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.

   yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe
   be freed which  was not allocated, this may give people a misunderstanding.
   Thanks.
I think it may be enough to add a comment, and the code does not need to be
modified.

Thanks.

Or even just leave the current code as is. A lot of kernel codes was 
wrote under the assumption that kfree() should deal with NULL.

Thanks


quoted
quoted
quoted
Here I adjust the initialization sequence and the check of vi->has_cvq
to slove this problem.

Fixes: 	122b84a1267a ("virtio-net: don't allocate control_buf if not
supported")
quoted
Signed-off-by: guodeqing <redacted>
---
   drivers/net/virtio_net.c | 20 ++++++++++----------
   1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index
9b6a4a875c55..894f894d3a29 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2691,7 +2691,8 @@ static void virtnet_free_queues(struct
virtnet_info *vi)

   	kfree(vi->rq);
   	kfree(vi->sq);
-	kfree(vi->ctrl);
+	if (vi->has_cvq)
+		kfree(vi->ctrl);
   }

   static void _free_receive_bufs(struct virtnet_info *vi) @@ -2870,13
+2871,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
   {
   	int i;

-	if (vi->has_cvq) {
-		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
-		if (!vi->ctrl)
-			goto err_ctrl;
-	} else {
-		vi->ctrl = NULL;
-	}
   	vi->sq = kcalloc(vi->max_queue_pairs, sizeof(*vi->sq), GFP_KERNEL);
   	if (!vi->sq)
   		goto err_sq;
@@ -2884,6 +2878,12 @@ static int virtnet_alloc_queues(struct
virtnet_info *vi)
quoted
   	if (!vi->rq)
   		goto err_rq;

+	if (vi->has_cvq) {
+		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
+		if (!vi->ctrl)
+			goto err_ctrl;
+	}
+
   	INIT_DELAYED_WORK(&vi->refill, refill_work);
   	for (i = 0; i < vi->max_queue_pairs; i++) {
   		vi->rq[i].pages = NULL;
@@ -2902,11 +2902,11 @@ static int virtnet_alloc_queues(struct
virtnet_info *vi)

   	return 0;

+err_ctrl:
+	kfree(vi->rq);
   err_rq:
   	kfree(vi->sq);
   err_sq:
-	kfree(vi->ctrl);
-err_ctrl:
   	return -ENOMEM;
   }
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Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization





  

    
Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

    

      From: Leon Romanovsky <leon@kernel.org>

      Date: 2021-06-02 05:50:51 
    

  

  
On Mon, May 24, 2021 at 10:37:14AM +0800, Jason Wang wrote:
在 2021/5/24 上午10:06, Xuan Zhuo 写道:
quoted
On Mon, 24 May 2021 01:48:53 +0000, Guodeqing (A) [off-list ref] wrote:
quoted
quoted
-----Original Message-----
From: Max Gurtovoy [mailto:mgurtovoy@nvidia.com]
Sent: Sunday, May 23, 2021 15:25
To: Guodeqing (A) <redacted>; mst@redhat.com
Cc: jasowang@redhat.com; davem@davemloft.net; kuba@kernel.org;
virtualization@lists.linux-foundation.org; netdev@vger.kernel.org
Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem


On 5/22/2021 11:02 AM, guodeqing wrote:
quoted
If the virtio_net device does not suppurt the ctrl queue feature, the
vi->ctrl was not allocated, so there is no need to free it.
you don't need this check.

from kfree doc:

"If @objp is NULL, no operation is performed."

This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.

   yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe
   be freed which  was not allocated, this may give people a misunderstanding.
   Thanks.
I think it may be enough to add a comment, and the code does not need to be
modified.

Thanks.

Or even just leave the current code as is. A lot of kernel codes was wrote
under the assumption that kfree() should deal with NULL.
It is not assumption but standard practice that can be seen as side
effect of "7) Centralized exiting of functions" section of coding-style.rst.

Thanks
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization





  

    
Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

    

      From: Jason Wang <hidden>

      Date: 2021-06-02 07:20:00 
    

  

  
在 2021/6/2 下午1:50, Leon Romanovsky 写道:
On Mon, May 24, 2021 at 10:37:14AM +0800, Jason Wang wrote:
quoted
在 2021/5/24 上午10:06, Xuan Zhuo 写道:
quoted
On Mon, 24 May 2021 01:48:53 +0000, Guodeqing (A) [off-list ref] wrote:
quoted
quoted
-----Original Message-----
From: Max Gurtovoy [mailto:mgurtovoy@nvidia.com]
Sent: Sunday, May 23, 2021 15:25
To: Guodeqing (A) <redacted>; mst@redhat.com
Cc: jasowang@redhat.com; davem@davemloft.net; kuba@kernel.org;
virtualization@lists.linux-foundation.org; netdev@vger.kernel.org
Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem


On 5/22/2021 11:02 AM, guodeqing wrote:
quoted
If the virtio_net device does not suppurt the ctrl queue feature, the
vi->ctrl was not allocated, so there is no need to free it.
you don't need this check.

from kfree doc:

"If @objp is NULL, no operation is performed."

This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.

    yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe
    be freed which  was not allocated, this may give people a misunderstanding.
    Thanks.
I think it may be enough to add a comment, and the code does not need to be
modified.

Thanks.
Or even just leave the current code as is. A lot of kernel codes was wrote
under the assumption that kfree() should deal with NULL.
It is not assumption but standard practice that can be seen as side
effect of "7) Centralized exiting of functions" section of coding-style.rst.

Thanks

I don't see the connection to the centralized exiting.

Something like:

if (foo)
     kfree(foo);

won't break the centralization.

Thanks


_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization





  

    
Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

    

      From: Leon Romanovsky <leon@kernel.org>

      Date: 2021-06-02 12:59:34 
    

  

  
On Wed, Jun 02, 2021 at 03:19:46PM +0800, Jason Wang wrote:
在 2021/6/2 下午1:50, Leon Romanovsky 写道:
quoted
On Mon, May 24, 2021 at 10:37:14AM +0800, Jason Wang wrote:
quoted
在 2021/5/24 上午10:06, Xuan Zhuo 写道:
quoted
On Mon, 24 May 2021 01:48:53 +0000, Guodeqing (A) [off-list ref] wrote:
quoted
quoted
-----Original Message-----
From: Max Gurtovoy [mailto:mgurtovoy@nvidia.com]
Sent: Sunday, May 23, 2021 15:25
To: Guodeqing (A) <redacted>; mst@redhat.com
Cc: jasowang@redhat.com; davem@davemloft.net; kuba@kernel.org;
virtualization@lists.linux-foundation.org; netdev@vger.kernel.org
Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem


On 5/22/2021 11:02 AM, guodeqing wrote:
quoted
If the virtio_net device does not suppurt the ctrl queue feature, the
vi->ctrl was not allocated, so there is no need to free it.
you don't need this check.

from kfree doc:

"If @objp is NULL, no operation is performed."

This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.

    yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe
    be freed which  was not allocated, this may give people a misunderstanding.
    Thanks.
I think it may be enough to add a comment, and the code does not need to be
modified.

Thanks.
Or even just leave the current code as is. A lot of kernel codes was wrote
under the assumption that kfree() should deal with NULL.
It is not assumption but standard practice that can be seen as side
effect of "7) Centralized exiting of functions" section of coding-style.rst.

Thanks

I don't see the connection to the centralized exiting.

Something like:

if (foo)
    kfree(foo);

won't break the centralization.
The key words are "side effect". Once you centralize everything, you
won't want to see "if (foo) kfree(foo)" spaghetti code.

Of course such construction doesn't break anything, but the idea is
to reduce useless code and not add it.

Thanks

Thanks


quoted
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Virtualization mailing list
Virtualization@lists.linux-foundation.org
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