linux-kernel - Re: [PATCH] udmabuf: validate ubuf->pagecount

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Date:   Wed, 12 Jan 2022 21:08:46 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     kraxel@...hat.com, sumit.semwal@...aro.org,
        christian.koenig@....com, daniel.vetter@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
        syzbot+2c56b725ec547fa9cb29@...kaller.appspotmail.com
Subject: Re: [PATCH] udmabuf: validate ubuf->pagecount

On 12/30/21 17:26, Pavel Skripkin wrote:
> Syzbot has reported GPF in sg_alloc_append_table_from_pages(). The
> problem was in ubuf->pages == ZERO_PTR.
> 
> ubuf->pagecount is calculated from arguments passed from user-space. If
> user creates udmabuf with list.size == 0 then ubuf->pagecount will be
> also equal to zero; it causes kmalloc_array() to return ZERO_PTR.
> 
> Fix it by validating ubuf->pagecount before passing it to
> kmalloc_array().
> 
> Fixes: fbb0de795078 ("Add udmabuf misc device")
> Reported-and-tested-by: syzbot+2c56b725ec547fa9cb29@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
> ---
> 

Gentle ping :)

> 
> ---
>   drivers/dma-buf/udmabuf.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index c57a609db75b..e7330684d3b8 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -190,6 +190,10 @@ static long udmabuf_create(struct miscdevice *device,
>   		if (ubuf->pagecount > pglimit)
>   			goto err;
>   	}
> +
> +	if (!ubuf->pagecount)
> +		goto err;
> +
>   	ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
>   				    GFP_KERNEL);
>   	if (!ubuf->pages) {

With regards,
Pavel Skripkin