linux-kernel - Re: [PATCH] b43legacy: Add checking for null for ssb_get

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Date:   Sat, 11 Feb 2023 14:45:26 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Natalia Petrova <n.petrova@...tech.ru>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-wireless@...r.kernel.org, b43-dev@...ts.infradead.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH] b43legacy: Add checking for null for
 ssb_get_devtypedata(dev)

On Fri, Feb 10, 2023 at 02:12:28PM +0300, Natalia Petrova wrote:
> Function ssb_get_devtypedata(dev) may return null (next call
> B43legacy_WARN_ON(!wl) is used for error handling, including null-value).
> Therefore, a check is added before calling b43legacy_wireless_exit(),
> where the argument containing this value is expected to be dereferenced.

I see that is true, however, in that case are resources leaked
due to the ieee80211_free_hw() call in b43legacy_wireless_exit()
not being made?

Moreover, aren't there also unguarded dereferences of wl:

1. In the call to b43legacy_one_core_attach(),
   which would branch to err_wireless_exit on failure.

2. In the call to schedule_work() just about the out: label.

For the record, and because it seems relevant to give contexxt,
b43legacy_probe() looks like this:

static int b43legacy_probe(struct ssb_device *dev,
                         const struct ssb_device_id *id)
{
        struct b43legacy_wl *wl;
        int err;
        int first = 0;

        wl = ssb_get_devtypedata(dev);
        if (!wl) {
                /* Probing the first core - setup common struct b43legacy_wl */
                first = 1;
                err = b43legacy_wireless_init(dev);
                if (err)
                        goto out;
                wl = ssb_get_devtypedata(dev);
                B43legacy_WARN_ON(!wl);
        }
        err = b43legacy_one_core_attach(dev, wl);
        if (err)
                goto err_wireless_exit;

        /* setup and start work to load firmware */
        INIT_WORK(&wl->firmware_load, b43legacy_request_firmware);
        schedule_work(&wl->firmware_load);

out:
        return err;

err_wireless_exit:
        if (first)
                b43legacy_wireless_exit(dev, wl);
        return err;
}


> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE
> 
> Fixes: 75388acd0cd8 ("[B43LEGACY]: add mac80211-based driver for legacy BCM43xx devices")
> Signed-off-by: Natalia Petrova <n.petrova@...tech.ru>
> ---
>  drivers/net/wireless/broadcom/b43legacy/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/net/wireless/broadcom/b43legacy/main.c
> index 760136638a95..1ae65679d704 100644
> --- a/drivers/net/wireless/broadcom/b43legacy/main.c
> +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
> @@ -3871,7 +3871,7 @@ static int b43legacy_probe(struct ssb_device *dev,
>  	return err;
>  
>  err_wireless_exit:
> -	if (first)
> +	if (first && wl)
>  		b43legacy_wireless_exit(dev, wl);
>  	return err;
>  }
> -- 
> 2.34.1
>