linux-kernel - Re: [PATCH net] net: mediatek: Fix potential NULL pointer dereference in dummy net

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Message-ID: <20240724174031.GF97837@kernel.org>
Date: Wed, 24 Jul 2024 18:40:31 +0100
From: Simon Horman <horms@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>,
	Mark Lee <Mark-MC.Lee@...iatek.com>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	leit@...a.com, Dan Carpenter <dan.carpenter@...aro.org>,
	"open list:MEDIATEK ETHERNET DRIVER" <netdev@...r.kernel.org>,
	"open list:ARM/Mediatek SoC support" <linux-kernel@...r.kernel.org>,
	"moderated list:ARM/Mediatek SoC support" <linux-arm-kernel@...ts.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH net] net: mediatek: Fix potential NULL pointer
 dereference in dummy net_device handling

On Wed, Jul 24, 2024 at 01:05:23AM -0700, Breno Leitao wrote:
> Move the freeing of the dummy net_device from mtk_free_dev() to
> mtk_remove().
> 
> Previously, if alloc_netdev_dummy() failed in mtk_probe(),
> eth->dummy_dev would be NULL. The error path would then call
> mtk_free_dev(), which in turn called free_netdev() assuming dummy_dev
> was allocated (but it was not), potentially causing a NULL pointer
> dereference.
> 
> By moving free_netdev() to mtk_remove(), we ensure it's only called when
> mtk_probe() has succeeded and dummy_dev is fully allocated. This
> addresses a potential NULL pointer dereference detected by Smatch[1].
> 
> Fixes: b209bd6d0bff ("net: mediatek: mtk_eth_sock: allocate dummy net_device dynamically")
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/all/4160f4e0-cbef-4a22-8b5d-42c4d399e1f7@stanley.mountain/ [1]
> Suggested-by: Dan Carpenter <dan.carpenter@...aro.org>
> Reviewed-by: Dan Carpenter <dan.carpenter@...aro.org>
> Signed-off-by: Breno Leitao <leitao@...ian.org>

Reviewed-by: Simon Horman <horms@...nel.org>

...