linux-kernel - Re: [PATCH net] mt76: mt7615: Fix memory leak in mt7615_mcu_wtbl_sta

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Message-ID: <aRW5phMmzul8wTn-@lore-desk>
Date: Thu, 13 Nov 2025 11:57:42 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Zilin Guan <zilin@....edu.cn>
Cc: angelogioacchino.delregno@...labora.com, jianhao.xu@....edu.cn,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-mediatek@...ts.infradead.org, linux-wireless@...r.kernel.org,
	matthias.bgg@...il.com, nbd@....name, ryder.lee@...iatek.com,
	sean.wang@...iatek.com, shayne.chen@...iatek.com
Subject: Re: [PATCH net] mt76: mt7615: Fix memory leak in
 mt7615_mcu_wtbl_sta_add()

> On Thu, Nov 13, 2025 at 08:17:09AM +0100, Lorenzo Bianconi wrote:
> > [-- Attachment #1: Type: text/plain, Size: 1475 bytes --]
> > 
> > > In mt7615_mcu_wtbl_sta_add(), an skb sskb is allocated. If the
> > > subsequent call to mt76_connac_mcu_alloc_wtbl_req() fails, the function
> > > returns an error without freeing sskb, leading to a memory leak.
> > > 
> > > Fix this by calling dev_kfree_skb() on sskb in the error handling path
> > > to ensure it is properly released.
> > > 
> > > Fixes: 99c457d902cf9 ("mt76: mt7615: move mt7615_mcu_set_bmc to mt7615_mcu_ops")
> > > Signed-off-by: Zilin Guan <zilin@....edu.cn>
> > > ---
> > >  drivers/net/wireless/mediatek/mt76/mt7615/mcu.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7615/mcu.c
> > > index 4064e193d4de..08ee2e861c4e 100644
> > > --- a/drivers/net/wireless/mediatek/mt76/mt7615/mcu.c
> > > +++ b/drivers/net/wireless/mediatek/mt76/mt7615/mcu.c
> > > @@ -874,8 +874,10 @@ mt7615_mcu_wtbl_sta_add(struct mt7615_phy *phy, struct ieee80211_vif *vif,
> > >  	wtbl_hdr = mt76_connac_mcu_alloc_wtbl_req(&dev->mt76, &msta->wcid,
> > >  						  WTBL_RESET_AND_SET, NULL,
> > >  						  &wskb);
> > > -	if (IS_ERR(wtbl_hdr))
> > > +	if (IS_ERR(wtbl_hdr)) {
> > > +		dev_kfree_skb(sskb);
> > 
> > Hi Zilin,
> > 
> > I can't see how this is useful since if mt76_connac_mcu_alloc_wtbl_req returns
> > an error, wskb will not be allocated.
> > 
> > Regards,
> > Lorenzo
> 
> Hi Lorenzo,
> 
> Thanks for your review.
> 
> You are correct that 'wskb' is not allocated in this error path. 
> However, my patch is intended to free 'sskb', which was allocated 
> earlier in the function. Without this change, 'sskb' is leaked if
> mt76_connac_mcu_alloc_wtbl_req() fails.
> 
> This approach is similar to the error handling logic later in the
> function, where a failure in sending one skb results in the other one
> being freed.
> 
> Hope this clarifies.

yes, right. I misread the code. I agree with the fix.

Acked-by: Lorenzo Bianconi <lorenzo@...nel.org>

> 
> > >  		return PTR_ERR(wtbl_hdr);
> > > +	}
> > >  
> > >  	if (enable) {
> > >  		mt76_connac_mcu_wtbl_generic_tlv(&dev->mt76, wskb, vif, sta,
> > > -- 
> > > 2.34.1
> > > 
> 
> Best Regards,
> Zilin Guan

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