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Date: Thu, 7 May 2026 07:29:54 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
Cc: Bobby Eshleman <bobbyeshleman@gmail.com>, Alexander Duyck
 <alexanderduyck@fb.com>, kernel-team@meta.com, Andrew Lunn
 <andrew+netdev@lunn.ch>, "David S. Miller" <davem@davemloft.net>, Eric
 Dumazet <edumazet@google.com>, Russell King <linux@armlinux.org.uk>,
 netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Bobby Eshleman
 <bobbyeshleman@meta.com>
Subject: Re: [PATCH net v2] eth: fbnic: fix double-free of PCS on phylink
 creation failure
Message-ID: <20260507072954.263ae8dd@kernel.org>
In-Reply-To: <20260507072453.5eec7051@kernel.org>
References: <20260504-fbnic-pcs-fix-v2-1-de45192821d9@meta.com>
	<6cec0c03-5bdc-4131-9899-bc5c77fba198@redhat.com>
	<20260507072453.5eec7051@kernel.org>
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On Thu, 7 May 2026 07:24:53 -0700 Jakub Kicinski wrote:
> On Thu, 7 May 2026 12:34:24 +0200 Paolo Abeni wrote:
> > > Clearing fbd->netdev to NULL avoids UAF in init_failure_mode where
> > > callers guard by checking !fbd->netdev, such as fbnic_mdio_read_pmd().
> > > These callers remain active even after a failed probe, so fdb->netdev
> > > still needs to be cleared.
> > > 
> > > Fixes: d0fe7104c795 ("fbnic: Replace use of internal PCS w/ Designware XPCS")
> > > Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>    
> > 
> > Note that sashiko-gemini spotted a pre-existing issue:
> > 
> > https://sashiko.dev/#/patchset/20260504-fbnic-pcs-fix-v2-1-de45192821d9%40meta.com
> > 
> > does not block this patch but could deserve a follow-up.  
> 
> fbd is a devlink priv, not netdev priv, touching it after free_netdev()
> is perfectly fine. I wish Gemini tried a *little* harder instead of
> guessing :| Sorry for not commenting earlier.

Ugh, not enough coffee. It's complaining about MDIO reads, I think
that's valid.