linux-kernel - Re: [PATCH] intel_th: avoid double free in error flow

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Date:   Wed, 20 Nov 2019 15:38:12 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Wen Yang <wenyang@...ux.alibaba.com>
Cc:     zhiche.yy@...baba-inc.com, xlpang@...ux.alibaba.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH] intel_th: avoid double free in error flow

Wen Yang <wenyang@...ux.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