netdev - Re: [PATCH net] macsec: Fix use-after-free while sending the offloading packet

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Message-ID: <Zw4uRHzqS05UBMCg@hog>
Date: Tue, 15 Oct 2024 10:56:36 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: Tariq Toukan <tariqt@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
	Saeed Mahameed <saeedm@...dia.com>, Gal Pressman <gal@...dia.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Jianbo Liu <jianbol@...dia.com>,
	Patrisious Haddad <phaddad@...dia.com>, Chris Mi <cmi@...dia.com>
Subject: Re: [PATCH net] macsec: Fix use-after-free while sending the
 offloading packet

2024-10-14, 12:07:20 +0300, Tariq Toukan wrote:
> From: Jianbo Liu <jianbol@...dia.com>
> 
> KASAN reports the following UAF. The metadata_dst, which is used to
> store the SCI value for macsec offload, is already freed by
> metadata_dst_free() in macsec_free_netdev(), while driver still use it
> for sending the packet.
> 
> To fix this issue, dst_release() is used instead to release
> metadata_dst. So it is not freed instantly in macsec_free_netdev() if
> still referenced by skb.

Ok. Then that packet is going to get dropped when it reaches the
driver, right? At this point the TXSA we need shouldn't be configured
anymore, so the driver/NIC won't be able to handle that skb. It would
be bad if we just sent the packet unencrypted.


> Fixes: 0a28bfd4971f ("net/macsec: Add MACsec skb_metadata_dst Tx Data path support")
> Signed-off-by: Jianbo Liu <jianbol@...dia.com>
> Reviewed-by: Patrisious Haddad <phaddad@...dia.com>
> Reviewed-by: Chris Mi <cmi@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  drivers/net/macsec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
> index 12d1b205f6d1..7076dedfa3be 100644
> --- a/drivers/net/macsec.c
> +++ b/drivers/net/macsec.c
> @@ -3817,7 +3817,7 @@ static void macsec_free_netdev(struct net_device *dev)
>  	struct macsec_dev *macsec = macsec_priv(dev);
>  
>  	if (macsec->secy.tx_sc.md_dst)

nit: dst_release checks that dst is not NULL, so we don't need this
test that I added in commit c52add61c27e ("macsec: don't free NULL
metadata_dst")

> -		metadata_dst_free(macsec->secy.tx_sc.md_dst);
> +		dst_release(&macsec->secy.tx_sc.md_dst->dst);
>  	free_percpu(macsec->stats);
>  	free_percpu(macsec->secy.tx_sc.stats);
>  
> -- 
> 2.44.0
> 

-- 
Sabrina