linux-kernel - Re: [PATCH v2] net: xfrm: Fix xfrm_address

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Message-ID: <55aca58a.a2c0e.188f54a2741.Coremail.linma@zju.edu.cn>
Date:   Mon, 26 Jun 2023 09:20:57 +0800 (GMT+08:00)
From:   "Lin Ma" <linma@....edu.cn>
To:     "Alexey Dobriyan" <adobriyan@...il.com>
Cc:     steffen.klassert@...unet.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, simon.horman@...igine.com
Subject: Re: [PATCH v2] net: xfrm: Fix xfrm_address_filter OOB read

Hello Alexey,

(sorry last mail just reply to one ..)

> 
> > + if (filter->splen >= (sizeof(xfrm_address_t) << 3) ||
> > + 	filter->dplen >= (sizeof(xfrm_address_t) << 3)) {
> 
> Please multiply by 8 if you want to multiply by 8.
> 

Thanks for reminding.

As I told in the commit message, this checking code is just copy from the function pfkey_dump (net/key/af_key.c), which like

	if ((xfilter->sadb_x_filter_splen >=
		(sizeof(xfrm_address_t) << 3)) ||
	    (xfilter->sadb_x_filter_dplen >=
		(sizeof(xfrm_address_t) << 3))) {
		mutex_unlock(&pfk->dump_lock);
		return -EINVAL;
	}

I think the left shift 3 is okay as the actual calculation on those lengths is right shift + left shift (see in addr_match() function).

> Should it be "splen > 8 * sizeof()" ?

Good question. It seems that the filter length is legal to reach the maximum length. So should I send another patch that allows the checking code in pfkey_dump (net/key/af_key.c) to change to > instead of >= ?

Regards
Lin