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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,
        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: <7e2a501f-955a-5bd1-f70d-ad69e7223981@linux.alibaba.com>
References: <20191119173447.2454-1-wenyang@linux.alibaba.com> <87y2wad7e5.fsf@ashishki-desk.ger.corp.intel.com> <7e2a501f-955a-5bd1-f70d-ad69e7223981@linux.alibaba.com>
Date:   Wed, 20 Nov 2019 15:38:12 +0200
Message-ID: <87v9red5x7.fsf@ashishki-desk.ger.corp.intel.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Wen Yang <wenyang@linux.alibaba.com> writes:

> Another example after a few lines lower:
>
>          err = device_add(&thdev->dev);
>
>          if (err) {
>                   put_device(&thdev->dev);
>                   goto fail_free_res;
>
>           }
>
> device_add() has increased the reference count,
>
> so when it returns an error, an additional call to put_device()
>
> is needed here to reduce the reference count.
>
> So the code in this place is correct.

No, device_add() drops its own extra reference in case of error (as it
should), so in "if (err) ..." branch we still only have just one
reference before it goes free.

Regards,
--
Alex