linux-kernel - Re: [syzbot] WARNING in dma_map

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Date:   Mon, 30 May 2022 18:10:44 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     syzbot <syzbot+3ba551855046ba3b3806@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in dma_map_sgtable (2)

On Mon, May 30, 2022 at 10:45:42PM +0800, Hillf Danton wrote:
> To queisce the warning, make udmabuf misc device dma capable by default.
> 
> #syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git   7e062cda7d90
> 
> --- y/drivers/dma-buf/udmabuf.c
> +++ u/drivers/dma-buf/udmabuf.c
> @@ -273,6 +273,14 @@ static long udmabuf_create(struct miscde
>  	if (IS_ERR(buf)) {
>  		ret = PTR_ERR(buf);
>  		goto err;
> +	} else {
> +		struct device *dev = ubuf->device->this_device;
> +
> +		if (!dev->dma_mask) {
> +			ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
> +			if (ret)
> +				goto err;
> +		}
>  	}
>  
>  	flags = 0;

Unrelated to your patch.  In this function do we not need to cleanup if
dma_buf_fd(buf, flags); fails?

After dma_buf_fd() then the fd is exported so we can't clean up, but it
should be okay to clean up if dma_buf_fd() fails.

regards,
dan carpenter