linux-kernel - Re: [PATCH RFC net] ps3/gelic: Fix possible NULL pointer dereference

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Message-ID: <13059273-4b1c-4e8e-a929-25fcf01bb727@infradead.org>
Date: Thu, 22 Feb 2024 16:23:08 +0900
From: Geoff Levand <geoff@...radead.org>
To: Simon Horman <horms@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin
 <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>,
 "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
 "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, Jeff Garzik <jeff@...zik.org>,
 Dan Carpenter <dan.carpenter@...aro.org>, netdev@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net] ps3/gelic: Fix possible NULL pointer dereference

Hi Simon,

On 2/22/24 01:56, Simon Horman wrote:
> Fix possible NULL pointer dereference in gelic_card_release_tx_chain()
> 
> The cited commit introduced a netdev variable to
> gelic_card_release_tx_chain() which is set unconditionally on each
> iteration of a for loop.
> 
> It is set to the value of tx_chain->tail->skb->dev.  However, in some
> cases it is assumed that tx_chain->tail->skb may be NULL. And if that
> occurs, setting netdev will cause a NULl pointer dereference.
> 
> Given the age of this code I do wonder if this can occur in practice.
> But to be on the safe side this patch assumes that it can and aims to
> avoid the dereference in the case where tx_chain->tail->skb may be NULL.

After 17+ years I never hit this, and never heard of anyone hitting it...

> Flagged by Smatch.
> Compile tested only.

Thanks for 'fixing' this.

Acked-by: Geoff Levand <geoff@...radead.org>