linux-kernel - Re: [PATCH net] xfrm: fix integer overflow in xfrm_replay_state_esn

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Message-ID: <32890a3f-1258-4c03-86e1-86c0e4e8e415@stanley.mountain>
Date: Wed, 22 Jan 2025 16:50:45 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Simon Horman <horms@...nel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@...unet.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] xfrm: fix integer overflow in
 xfrm_replay_state_esn_len()

On Wed, Jan 22, 2025 at 04:16:48PM +0300, Dan Carpenter wrote:
> On Wed, Jan 22, 2025 at 12:39:36PM +0000, Simon Horman wrote:
> > > The one caller that I didn't modify was xfrm_sa_len().  That's a bit
> > > complicated and also I'm kind of hoping that we don't handle user
> > > controlled data in that function?  The place where we definitely are
> > > handling user data is in xfrm_alloc_replay_state_esn() and this patch
> > > fixes that.
> > 
> > Yes, that is a bit "complex".
> > 
> 
> I don't have a reason to suspect xfrm_sa_len() but if we were to write
> a paranoid version of it then I've written that draft below.  I stole
> Herbert's xfrm_kblen2klen() function[1].  Also the nlmsg_new() function
> would need to be updated as well.
> 
> https://lore.kernel.org/all/Z2KZC71JZ0QnrhfU@gondor.apana.org.au/
> 
> regards,
> dan carpenter
> 
> diff --git a/include/net/netlink.h b/include/net/netlink.h
> index e015ffbed819..ca7a8152e6d4 100644
> --- a/include/net/netlink.h
> +++ b/include/net/netlink.h
> @@ -1015,6 +1015,8 @@ static inline struct nlmsghdr *nlmsg_put_answer(struct sk_buff *skb,
>   */
>  static inline struct sk_buff *nlmsg_new(size_t payload, gfp_t flags)
>  {
> +	if (payload > INT_MAX)
> +		return NULL;
>  	return alloc_skb(nlmsg_total_size(payload), flags);
>  }

Actually, this chunk is necessary.  Let me sent that by itself.

regards,
dan carpenter