netdev - Re: [PATCH v2] net: ipv6: fix use-after-free Read in __xfrm6_tunnel_spi

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Message-Id: <20200728.173629.741539582090080322.davem@davemloft.net>
Date:   Tue, 28 Jul 2020 17:36:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     bkkarthik@...u.pes.edu
Cc:     steffen.klassert@...unet.com, herbert@...dor.apana.org.au,
        kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v2] net: ipv6: fix use-after-free Read in
 __xfrm6_tunnel_spi_lookup

From: B K Karthik <bkkarthik@...u.pes.edu>
Date: Sun, 26 Jul 2020 08:38:55 +0530

> @@ -103,10 +103,10 @@ static int __xfrm6_tunnel_spi_check(struct net *net, u32 spi)
>  {
>  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
>  	struct xfrm6_tunnel_spi *x6spi;
> -	int index = xfrm6_tunnel_spi_hash_byspi(spi);
> +	int index = xfrm6_tunnel_spi_hash_byaddr((const xfrm_address_t *)spi);

We can cast this a thousand times to make the compiler quiet, but the
fact is that this function does not expect an integer SPI as an
argument.

It expects a protocol address.

Please stop forcing this fix, I fear you don't understand how this code
works.  Come back to us when you do.

Thank you.