netdev - Re: [PATCH net] atm: null pointer dereference when both entry and holding

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Message-ID: <c1b104c0-7b06-48fd-9463-9330b17678a2@redhat.com>
Date: Thu, 20 Mar 2025 10:36:30 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: pwn9uin@...il.com, "David S . Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
 Minjoong Kim <alswnd4123@...look.kr>
Subject: Re: [PATCH net] atm: null pointer dereference when both entry and
 holding_time are NULL.

On 3/14/25 1:34 AM, pwn9uin@...il.com wrote:
> From: Minjoong Kim <alswnd4123@...look.kr>
> 
> When MPOA_cache_impos_rcvd() receives the msg, it can trigger
> Null Pointer Dereference Vulnerability if both entry and
> holding_time are NULL. Because there is only for the situation
> where entry is NULL and holding_time exists, it can be passed
> when both entry and holding_time are NULL. If these are NULL,
> the entry will be passd to eg_cache_put() as parameter and
> it is referenced by entry->use code in it.
> 
> Signed-off-by: Minjoong Kim <alswnd4123@...look.kr>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

Please include the full splat for such UaF in the commit message

> ---
>  net/atm/mpc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/atm/mpc.c b/net/atm/mpc.c
> index 324e3ab96bb3..7fb854ea47dc 100644
> --- a/net/atm/mpc.c
> +++ b/net/atm/mpc.c
> @@ -1314,6 +1314,9 @@ static void MPOA_cache_impos_rcvd(struct k_message *msg,
>  	holding_time = msg->content.eg_info.holding_time;
>  	dprintk("(%s) entry = %p, holding_time = %u\n",
>  		mpc->dev->name, entry, holding_time);
> +	if (entry == NULL && !holding_time) {
> +		return;

Brackets are unneeded here.

Thanks,

Paolo