linux-kernel - Re: [PATCH 1/2] uio_hv_generic: Fix a memory leak in error handling paths

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Message-ID: <20210511095227.ggrl3z6otjanwffz@liuwe-devbox-debian-v2>
Date:   Tue, 11 May 2021 09:52:27 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com,
        gregkh@...uxfoundation.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/2] uio_hv_generic: Fix a memory leak in error handling
 paths

On Sun, May 09, 2021 at 09:13:03AM +0200, Christophe JAILLET wrote:
> If 'vmbus_establish_gpadl()' fails, the (recv|send)_gpadl will not be
> updated and 'hv_uio_cleanup()' in the error handling path will not be
> able to free the corresponding buffer.
> 
> In such a case, we need to free the buffer explicitly.
> 
> Fixes: cdfa835c6e5e ("uio_hv_generic: defer opening vmbus until first use")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> Before commit cdfa835c6e5e, the 'vfree' were done unconditionally
> in 'hv_uio_cleanup()'.
> So, another way for fixing the potential leak is to modify
> 'hv_uio_cleanup()' and revert to the previous behavior.
> 

I think this is cleaner.

Stephen, you authored cdfa835c6e5e. What do you think?

Christophe, OOI how did you discover these issues?

> I don't know the underlying reason for this change so I don't know which is
> the best way to fix this error handling path. Unless there is a specific
> reason, changing 'hv_uio_cleanup()' could be better because it would keep
> the error handling path of the probe cleaner, IMHO.
> ---
>  drivers/uio/uio_hv_generic.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 0330ba99730e..eebc399f2cc7 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -296,8 +296,10 @@ hv_uio_probe(struct hv_device *dev,
>  
>  	ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
>  				    RECV_BUFFER_SIZE, &pdata->recv_gpadl);
> -	if (ret)
> +	if (ret) {
> +		vfree(pdata->recv_buf);
>  		goto fail_close;
> +	}
>  
>  	/* put Global Physical Address Label in name */
>  	snprintf(pdata->recv_name, sizeof(pdata->recv_name),
> @@ -316,8 +318,10 @@ hv_uio_probe(struct hv_device *dev,
>  
>  	ret = vmbus_establish_gpadl(channel, pdata->send_buf,
>  				    SEND_BUFFER_SIZE, &pdata->send_gpadl);
> -	if (ret)
> +	if (ret) {
> +		vfree(pdata->send_buf);
>  		goto fail_close;
> +	}
>  
>  	snprintf(pdata->send_name, sizeof(pdata->send_name),
>  		 "send:%u", pdata->send_gpadl);
> -- 
> 2.30.2
>