linux-kernel - Re: [PATCH v3] media: rga: fix NULL pointer dereferences, use-after-free, memory leak

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Date:   Thu, 28 Mar 2019 10:00:09 -0500
From:   Kangjie Lu <kjlu@....edu>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     pakki001@....edu, Jacob chen <jacob2.chen@...k-chips.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>, linux-media@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] media: rga: fix NULL pointer dereferences,
 use-after-free, memory leak


On 3/28/19 9:47 AM, Hans Verkuil wrote:
> Hi Kangjie,
>
> Unfortunately there are more issues with the cleanup sequence in
> this probe function:
>
> On 3/14/19 6:03 AM, Kangjie Lu wrote:
>> 1. dma_alloc_attrs, __get_free_pages can fail and return NULL.
>> Further uses of their return values lead to NULL pointer
>> dereferences
>>
>> 2. In the error-handling path, video_unregister_device uses
>> "rga->vfd" which has been freed by video_device_release
>>
>> 3. The error handling for v4l2_m2m_init and video_register_device
>> has memory-leak issues
>>
>> The patch fixes the above issues.
>>
>> Signed-off-by: Kangjie Lu <kjlu@....edu>
>> ---
>>   drivers/media/platform/rockchip/rga/rga.c | 26 ++++++++++++++++++++---
>>   1 file changed, 23 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
>> index 5c653287185f..468365ceb99d 100644
>> --- a/drivers/media/platform/rockchip/rga/rga.c
>> +++ b/drivers/media/platform/rockchip/rga/rga.c
>> @@ -889,11 +889,24 @@ static int rga_probe(struct platform_device *pdev)
>>   	rga->cmdbuf_virt = dma_alloc_attrs(rga->dev, RGA_CMDBUF_SIZE,
>>   					   &rga->cmdbuf_phy, GFP_KERNEL,
>>   					   DMA_ATTR_WRITE_COMBINE);
>> +	if (!rga->cmdbuf_virt) {
>> +		ret = -ENOMEM;
>> +		goto unreg_video_dev;
> Actually, the unreg_video_dev label makes no sense: if the video device
> is successfully registered, then probe() returns 0. So you never need to
> unregister the video device again. You *do* need to release it with
> video_device_release().
>
> So this should be a goto rel_vdev.
>
> And the cleanup sequence at the end also fails to call v4l2_m2m_release().
>
> Can you make v4?


Thanks for the feedback. Will send a v4.


>
> Thanks!
>
> 	Hans
>
>> +	}
>>   
>>   	rga->src_mmu_pages =
>>   		(unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);
>> +	if (!rga->src_mmu_pages) {
>> +		ret = -ENOMEM;
>> +		goto free_dma_attrs;
>> +	}
>> +
>>   	rga->dst_mmu_pages =
>>   		(unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);
>> +	if (!rga->dst_mmu_pages) {
>> +		ret = -ENOMEM;
>> +		goto free_dst_pages;
>> +	}
>>   
>>   	def_frame.stride = (def_frame.width * def_frame.fmt->depth) >> 3;
>>   	def_frame.size = def_frame.stride * def_frame.height;
>> @@ -901,7 +914,7 @@ static int rga_probe(struct platform_device *pdev)
>>   	ret = video_register_device(vfd, VFL_TYPE_GRABBER, -1);
>>   	if (ret) {
>>   		v4l2_err(&rga->v4l2_dev, "Failed to register video device\n");
>> -		goto rel_vdev;
>> +		goto free_pages;
>>   	}
>>   
>>   	v4l2_info(&rga->v4l2_dev, "Registered %s as /dev/%s\n",
>> @@ -909,10 +922,17 @@ static int rga_probe(struct platform_device *pdev)
>>   
>>   	return 0;
>>   
>> -rel_vdev:
>> -	video_device_release(vfd);
>> +free_pages:
>> +	free_pages((unsigned long)rga->src_mmu_pages, 3);
>> +free_dst_pages:
>> +	free_pages((unsigned long)rga->dst_mmu_pages, 3);
>> +free_dma_attrs:
>> +	dma_free_attrs(rga->dev, RGA_CMDBUF_SIZE, rga->cmdbuf_virt,
>> +		       rga->cmdbuf_phy,
>> +		       DMA_ATTR_WRITE_COMBINE);
>>   unreg_video_dev:
>>   	video_unregister_device(rga->vfd);
>> +	video_device_release(vfd);
>>   unreg_v4l2_dev:
>>   	v4l2_device_unregister(&rga->v4l2_dev);
>>   err_put_clk:
>>