linux-kernel - Re: [PATCH v3 2/7] firmware: coreboot: Unmap ioregion on failure

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Message-ID: <20180809174936.GC129285@ban.mtv.corp.google.com>
Date:   Thu, 9 Aug 2018 10:49:38 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Wei-Ning Huang <wnhuang@...omium.org>,
        Julius Werner <jwerner@...omium.org>,
        Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH v3 2/7] firmware: coreboot: Unmap ioregion on failure

On Thu, Aug 09, 2018 at 10:17:17AM -0700, Stephen Boyd wrote:
> Both callers of coreboot_table_init() ioremap the pointer that comes in
> but they don't unmap the memory on failure. Both of them also fail probe
> immediately with the return value of coreboot_table_init(), leaking a
> mapping when it fails. Plug the leak so the mapping isn't left unused.
> 
> Cc: Wei-Ning Huang <wnhuang@...omium.org>
> Cc: Julius Werner <jwerner@...omium.org>
> Cc: Brian Norris <briannorris@...omium.org>
> Cc: Samuel Holland <samuel@...lland.org>
> Fixes: 570d30c2823f ("firmware: coreboot: Expose the coreboot table as a bus")

I suppose this is fair, since that commit introduced error paths and
didn't clean them up. But one warning below:

> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/firmware/google/coreboot_table.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
> index 19db5709ae28..0d3e140444ae 100644
> --- a/drivers/firmware/google/coreboot_table.c
> +++ b/drivers/firmware/google/coreboot_table.c
> @@ -138,6 +138,9 @@ int coreboot_table_init(struct device *dev, void __iomem *ptr)
>  		ptr_entry += entry.size;
>  	}
>  
> +	if (ret)
> +		iounmap(ptr);

This works because no sub-driver is using this mapping any more (i.e.,
because we killed coreboot_table_find()). Otherwise, we'd need to
explicitly kill all the sub-devices first. IOW, if this gets backported
to older kernels, it would need to go along with this and its other
dependencies:

b616cf53aa7a firmware: coreboot: Remove unused coreboot_table_find

But I guess that's a question for -stable. Or, we remove the 'Fixes'
tag? Or add another tag, to list other dependencies? Or just ignore it.

But for this change as applied to mainline:

Reviewed-by: Brian Norris <briannorris@...omium.org>

> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(coreboot_table_init);
> -- 
> Sent by a computer through tubes
>