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From:   Alexander Shishkin <alexander.shishkin@linux.intel.com>
To:     Wen Yang <wenyang@linux.alibaba.com>
Cc:     zhiche.yy@alibaba-inc.com, xlpang@linux.alibaba.com,
        Wen Yang <wenyang@linux.alibaba.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com
Subject: Re: [PATCH] intel_th: avoid double free in error flow
In-Reply-To: <20191119173447.2454-1-wenyang@linux.alibaba.com>
References: <20191119173447.2454-1-wenyang@linux.alibaba.com>
Date:   Wed, 20 Nov 2019 15:06:26 +0200
Message-ID: <87y2wad7e5.fsf@ashishki-desk.ger.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Wen Yang <wenyang@linux.alibaba.com> writes:

> There is a possible double free issue in intel_th_subdevice_alloc:
>
> 651         err = intel_th_device_add_resources(thdev, res, subdev->nres);
> 652         if (err) {
> 653                 put_device(&thdev->dev);
> 654                 goto fail_put_device;     ---> freed
> 655         }
> ...
> 687 fail_put_device:
> 688         put_device(&thdev->dev);          ---> double freed
> 689
>
> This patch fix it by removing the unnecessary put_device().

Unnecessary is a too generous term here.

> Fixes: a753bfcfdb1f ("intel_th: Make the switch allocate its subdevices")
> Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-kernel@vger.kernel.org

Cc: stable@ is missing.

> ---
>  drivers/hwtracing/intel_th/core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
> index d5c1821..98d195c 100644
> --- a/drivers/hwtracing/intel_th/core.c
> +++ b/drivers/hwtracing/intel_th/core.c
> @@ -649,10 +649,8 @@ static inline void intel_th_request_hub_module_flush(struct intel_th *th)
>  	}
>  
>  	err = intel_th_device_add_resources(thdev, res, subdev->nres);
> -	if (err) {
> -		put_device(&thdev->dev);
> +	if (err)
>  		goto fail_put_device;
> -	}

What about the second instance of the same problem a few lines lower?

Thanks,
--
Alex