Re: [PATCH net v3 3/5] net: mana: Guard mana_remove against double invocation

[Simon Horman <horms@kernel.org>]

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---
net: mana: Guard mana_remove against double invocation

If PM resume fails (e.g., mana_attach() returns an error), mana_probe()
calls mana_remove(), which tears down the device and sets
gd->gdma_context = NULL and gd->driver_data = NULL. However, a failed
resume callback does not automatically unbind the driver. When the device
is eventually unbound, mana_remove() is invoked a second time. Without a
NULL check, it dereferences gc->dev with gc == NULL, causing a kernel
panic. Add an early return if gdma_context or driver_data is NULL so the
second invocation is harmless.

> Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")

The Fixes: tag points to ca9c54d2d6a5, which introduced mana_remove()
without NULL checks. However, the exploitable double invocation scenario
was actually introduced by commit 635096a86edb ("net: mana: Support
hibernation and kexec"), which added suspend/resume support and made
mana_probe() call mana_remove() on error.

Should the Fixes: tag be:

Fixes: 635096a86edb ("net: mana: Support hibernation and kexec")

> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index 9d095a6fb56c..2ab7c89e2fed 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -3685,11 +3685,16 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
>  	struct gdma_context *gc = gd->gdma_context;
>  	struct mana_context *ac = gd->driver_data;
>  	struct mana_port_context *apc;
> -	struct device *dev = gc->dev;
> +	struct device *dev;
>  	struct net_device *ndev;
>  	int err;
>  	int i;
>
> +	if (!gc || !ac)
> +		return;
> +
> +	dev = gc->dev;
> +
>  	disable_work_sync(&ac->link_change_work);
>  	cancel_delayed_work_sync(&ac->gf_stats_work);