linux-kernel - Re: [PATCH v2] vfio: Clear the caps->buf to NULL after free

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Date:   Tue, 28 Jun 2022 09:50:13 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Schspa Shi <schspa@...il.com>
Cc:     cohuck@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vfio: Clear the caps->buf to NULL after free

On Tue, 28 Jun 2022 23:24:29 +0800
Schspa Shi <schspa@...il.com> wrote:

> API vfio_info_cap_add will free caps->buf, clear it to NULL after
> free.

Should this be something like:

    On buffer resize failure, vfio_info_cap_add() will free the buffer,
    report zero for the size, and return -ENOMEM.  As additional
    hardening, also clear the buffer pointer to prevent any chance of a
    double free.

Thanks,
Alex
 
> Signed-off-by: Schspa Shi <schspa@...il.com>
> ---
>  drivers/vfio/vfio.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 61e71c1154be..a0fb93866f61 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -1812,6 +1812,7 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
>  	buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
>  	if (!buf) {
>  		kfree(caps->buf);
> +		caps->buf = NULL;
>  		caps->size = 0;
>  		return ERR_PTR(-ENOMEM);
>  	}