LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	PanBian <bianpan2016@163.com>
Cc: Juergen Gross <jgross@suse.com>,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Subject: Re: [Xen-devel] [PATCH] pvcalls-front: fixes incorrect error handling
Date: Tue, 27 Nov 2018 15:57:39 -0500	[thread overview]
Message-ID: <0af126ad-1a74-e4c7-d74f-658a46757b9d@oracle.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1811271233550.4577@sstabellini-ThinkPad-X260>

On 11/27/18 3:37 PM, Stefano Stabellini wrote:
> On Tue, 27 Nov 2018, PanBian wrote:
>> On Mon, Nov 26, 2018 at 03:31:39PM -0500, Boris Ostrovsky wrote:
>>> On 11/21/18 9:07 PM, Pan Bian wrote:
>>>> kfree() is incorrectly used to release the pages allocated by
>>>> __get_free_page() and __get_free_pages(). Use the matching deallocators
>>>> i.e., free_page() and free_pages(), respectively.
>>>>
>>>> Signed-off-by: Pan Bian <bianpan2016@163.com>
>>>> ---
>>>>  drivers/xen/pvcalls-front.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
>>>> index 2f11ca7..77224d8 100644
>>>> --- a/drivers/xen/pvcalls-front.c
>>>> +++ b/drivers/xen/pvcalls-front.c
>>>> @@ -385,8 +385,8 @@ static int create_active(struct sock_mapping *map, int *evtchn)
>>>>  out_error:
>>>>  	if (*evtchn >= 0)
>>>>  		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
>>>> -	kfree(map->active.data.in);
>>>> -	kfree(map->active.ring);
>>>> +	free_pages((unsigned long)map->active.data.in, PVCALLS_RING_ORDER);
>>> Is map->active.data.in guaranteed to be NULL when entering this routine?
>> I am not sure yet. Sorry for that. I observed the mismatches between
>> __get_free_page and kfree, and submitted the patch.
>>
>> But I think your consideration is reasonable. A better solution is to
>> directly free bytes, a local variable that holds __get_free_pages return
>> value. If you agree, I will rewrite the patch.
> Like Boris said, map->active.ring and map->active.data.in are not
> guaranteed to be NULL or != NULL here. For instance,map->active.ring can
> be != NULL and map->active.data.in can be NULL. However, free_pages and
> free_page should be able to cope with it, the same way that kfree is
> able to cope with it?

If map->active.data.in can be non-NULL on entry to this routine then I
think this has been a problem all along. Pan's suggestion to use bytes
for freeing is going to solve this (assuming bytes will be initialized
to NULL).


-boris


>
>>> -boris
>>>
>>>> +	free_page((unsigned long)map->active.ring);
>>>>  	return ret;
>>>>  }
>>>>  


  reply	other threads:[~2018-11-27 20:58 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-22  2:07 Pan Bian
2018-11-26 20:31 ` [Xen-devel] " Boris Ostrovsky
2018-11-27  0:58   ` PanBian
2018-11-27 20:37     ` Stefano Stabellini
2018-11-27 20:57       ` Boris Ostrovsky [this message]
2018-11-27 21:08         ` Stefano Stabellini
2018-11-27 22:47           ` Boris Ostrovsky
2018-11-27 22:51             ` Stefano Stabellini
2018-11-29 16:54 ` Juergen Gross

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=0af126ad-1a74-e4c7-d74f-658a46757b9d@oracle.com \
    --to=boris.ostrovsky@oracle.com \
    --cc=bianpan2016@163.com \
    --cc=jgross@suse.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=sstabellini@kernel.org \
    --cc=xen-devel@lists.xenproject.org \
    --subject='Re: [Xen-devel] [PATCH] pvcalls-front: fixes incorrect error handling' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).