linux-kernel - Re: [Patch net, v2] net: xfrm: skip policies marked as dead while reinserting policies

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Message-ID: <20230815080557.GK22185@unreal>
Date:   Tue, 15 Aug 2023 11:05:57 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Florian Westphal <fw@...len.de>,
        Dong Chenchen <dongchenchen2@...wei.com>,
        steffen.klassert@...unet.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        timo.teras@....fi, yuehaibing@...wei.com, weiyongjun1@...wei.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch net, v2] net: xfrm: skip policies marked as dead while
 reinserting policies

On Tue, Aug 15, 2023 at 03:51:44PM +0800, Herbert Xu wrote:
> On Tue, Aug 15, 2023 at 10:30:33AM +0300, Leon Romanovsky wrote:
> >
> > But policy has, and we are not interested in validity of it as first
> > check in if (...) will be true for policy->walk.dead.
> > 
> > So it is safe to call to dir = xfrm_policy_id2dir(policy->index) even
> > for dead policy.
> 
> If you dereference policy->index on a walker object it will read memory
> before the start of the walker object.  That could do anything, perhaps
> even triggering a page fault.

Where do you see walker object? xfrm_policy_id2dir() is called on policy
object, which is defined as "struct xfrm_policy".

Thanks

> 
> Cheers,
> -- 
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt