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Subject: Re: [PATCH v5] remoteproc: Fix NULL pointer dereference in
 rproc_virtio_notify
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
CC:     Nikita Shubin <nshubin@topcon.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Ohad Ben-Cohen <ohad@wizery.com>,
        "linux-remoteproc@vger.kernel.org" <linux-remoteproc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
References: <20200306070325.15232-1-NShubin@topcon.com>
 <20200306072452.24743-1-NShubin@topcon.com>
 <6c7ef4f2-6f71-c2fb-b2e9-ad7cbeb7cfbc@st.com>
 <20200310120846.GA19430@topcon.com>
 <507197c5412e4b438aeb5c527be74b3a@SFHDAG3NODE1.st.com>
 <20200311200107.GZ1214176@minitux>
From:   Arnaud POULIQUEN <arnaud.pouliquen@st.com>
Message-ID: <f6de2571-3541-7004-bc57-92cb3fef2c71@st.com>
Date:   Tue, 17 Mar 2020 15:24:53 +0100
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Hi Bjorn

On 3/11/20 9:01 PM, Bjorn Andersson wrote:
> On Tue 10 Mar 06:19 PDT 2020, Arnaud POULIQUEN wrote:
> 
>>
>>
>>> -----Original Message-----
>>> From: linux-remoteproc-owner@vger.kernel.org <linux-remoteproc-
>>> owner@vger.kernel.org> On Behalf Of Nikita Shubin
>>> Sent: mardi 10 mars 2020 13:09
>>> To: Arnaud POULIQUEN <arnaud.pouliquen@st.com>
>>> Cc: stable@vger.kernel.org; Ohad Ben-Cohen <ohad@wizery.com>; Bjorn
>>> Andersson <bjorn.andersson@linaro.org>; linux-
>>> remoteproc@vger.kernel.org; linux-kernel@vger.kernel.org; Mathieu Poirier
>>> <mathieu.poirier@linaro.org>
>>> Subject: Re: [PATCH v5] remoteproc: Fix NULL pointer dereference in
>>> rproc_virtio_notify
>>>
>>> On Mon, Mar 09, 2020 at 03:22:24PM +0100, Arnaud POULIQUEN wrote:
>>>> Hi,
>>>>
>>>> sorry for the late answer...
>>>>
>>>> On 3/6/20 8:24 AM, Nikita Shubin wrote:
>>>>> Undefined rproc_ops .kick method in remoteproc driver will result in
>>>>> "Unable to handle kernel NULL pointer dereference" in
>>>>> rproc_virtio_notify, after firmware loading if:
>>>>>
>>>>>  1) .kick method wasn't defined in driver
>>>>>  2) resource_table exists in firmware and has "Virtio device entry"
>>>>> defined
>>>>>
>>>>> Let's refuse to register an rproc-induced virtio device if no kick
>>>>> method was defined for rproc.
>>>>>

[...]

>>>>>
>>>>> Signed-off-by: Nikita Shubin <NShubin@topcon.com>
>>>>> Fixes: 7a186941626d ("remoteproc: remove the single rpmsg vdev
>>>>> limitation")
>>>>> Cc: stable@vger.kernel.org
>>>>> ---
>>>>>  drivers/remoteproc/remoteproc_virtio.c | 7 +++++++
>>>>>  1 file changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/drivers/remoteproc/remoteproc_virtio.c
>>>>> b/drivers/remoteproc/remoteproc_virtio.c
>>>>> index 8c07cb2ca8ba..31a62a0b470e 100644
>>>>> --- a/drivers/remoteproc/remoteproc_virtio.c
>>>>> +++ b/drivers/remoteproc/remoteproc_virtio.c
>>>>> @@ -334,6 +334,13 @@ int rproc_add_virtio_dev(struct rproc_vdev
>>> *rvdev, int id)
>>>>>  	struct rproc_mem_entry *mem;
>>>>>  	int ret;
>>>>>
>>>>> +	if (rproc->ops->kick == NULL) {
>>>>> +		ret = -EINVAL;
>>>>> +		dev_err(dev, ".kick method not defined for %s",
>>>>> +				rproc->name);
>>>>> +		goto out;
>>>>> +	}
>>>>> +
>>>> Should the kick ops be mandatory for all the platforms? How about making
>>> it optional instead?
>>>
>>> Hi, Arnaud.
>>>
>>> It is not mandatory, currently it must be provided if specified vdev entry is in
>>> resourse table. Otherwise it looks like there is no point in creating vdev.
>>
>> Yes, my question was about having it optional for vdev also. A platform could implement the vdev
>> without kick mechanism but by polling depending due to hardware capability...
>> This could be an alternative avoiding to implement a dummy function in platform driver.
>>
> 
> Is this a real thing or a theoretical suggestion?
Only a theoretical suggestion, trigged by the IMX platform patchset which implement a "temporary" dummy kick.
and based on OpenAMP lib implementation which does not request a doorbell.
Anyway no issue to keep it mandatory here. 

Regards,
Arnaud

> 
> Regards,
> Bjorn
> 
>> Anyway it just a proposal that makes sense from MPOV. If Bjorn is ok with your patch, nothing blocking on my side.
>>
>> Regards
>> Arnaud
>>
>>>
>>>
>>>>
>>>> Regards,
>>>> Arnaud
>>>>
>>>>>  	/* Try to find dedicated vdev buffer carveout */
>>>>>  	mem = rproc_find_carveout_by_name(rproc, "vdev%dbuffer",
>>> rvdev->index);
>>>>>  	if (mem) {
>>>>>