linux-kernel - Re: [PATCH] staging: rts5208: add check on NULL before dereference

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Date:   Sat, 09 Jun 2018 12:58:27 -0400
From:   okaya@...eaurora.org
To:     Anton Vasilyev <vasilyev@...ras.ru>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Gaurav Pathak <gauravpathak129@...il.com>,
        Hannes Reinecke <hare@...e.de>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] staging: rts5208: add check on NULL before dereference

On 2018-06-09 12:38, Anton Vasilyev wrote:
> If rtsx_probe fails to allocate dev->chip, then NULL pointer
> dereference occurs at rtsx_release_resources().
> 
> Patch adds checks chip on NULL before its dereference at
> rtsx_release_resources and passing with dereference inside
> rtsx_release_chip.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Anton Vasilyev <vasilyev@...ras.ru>
> ---
>  drivers/staging/rts5208/rtsx.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/rts5208/rtsx.c 
> b/drivers/staging/rts5208/rtsx.c
> index 70e0b8623110..952dd0d580cf 100644
> --- a/drivers/staging/rts5208/rtsx.c
> +++ b/drivers/staging/rts5208/rtsx.c
> @@ -623,12 +623,13 @@ static void rtsx_release_resources(struct 
> rtsx_dev *dev)
> 

I think you should bail out if dev->chip is null rather than adding 
conditiinals.


>  	if (dev->irq > 0)
>  		free_irq(dev->irq, (void *)dev);
> -	if (dev->chip->msi_en)
> +	if (dev->chip && dev->chip->msi_en)
>  		pci_disable_msi(dev->pci);
>  	if (dev->remap_addr)
>  		iounmap(dev->remap_addr);
> +	if (dev->chip)
> +		rtsx_release_chip(dev->chip);
> 
> -	rtsx_release_chip(dev->chip);
>  	kfree(dev->chip);
>  }