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From:   Gabriel Ryan <gabe@cs.columbia.edu>
Date:   Mon, 22 Aug 2022 12:19:54 -0400
Message-ID: <CALbthtcfPn5qc0HecmK9iN-o+ZWDVid4bwzZJmO2sthw3fKFBQ@mail.gmail.com>
Subject: Re: [PATCH] af_key: Do not call xfrm_probe_algs in parallel
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Abhishek Shah <abhishek.shah@columbia.edu>, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, netdev@vger.kernel.org,
        pabeni@redhat.com, steffen.klassert@secunet.com,
        linux-kernel@vger.kernel.org, Fan Du <fan.du@windriver.com>,
        Steffen Klassert <klassert@kernel.org>
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We can confirm we tested this patch and it prevents the race we
detected in xfrm_ealg_get_byname / xfrm_probe_algs.

Best,

Gabe


On Thu, Aug 4, 2022 at 6:03 AM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> When namespace support was added to xfrm/afkey, it caused the
> previously single-threaded call to xfrm_probe_algs to become
> multi-threaded.  This is buggy and needs to be fixed with a mutex.
>
> Reported-by: Abhishek Shah <abhishek.shah@columbia.edu>
> Fixes: 283bc9f35bbb ("xfrm: Namespacify xfrm state/policy locks")
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/net/key/af_key.c b/net/key/af_key.c
> index fb16d7c4e1b8..20e73643b9c8 100644
> --- a/net/key/af_key.c
> +++ b/net/key/af_key.c
> @@ -1697,9 +1697,12 @@ static int pfkey_register(struct sock *sk, struct sk_buff *skb, const struct sad
>                 pfk->registered |= (1<<hdr->sadb_msg_satype);
>         }
>
> +       mutex_lock(&pfkey_mutex);
>         xfrm_probe_algs();
>
>         supp_skb = compose_sadb_supported(hdr, GFP_KERNEL | __GFP_ZERO);
> +       mutex_unlock(&pfkey_mutex);
> +
>         if (!supp_skb) {
>                 if (hdr->sadb_msg_satype != SADB_SATYPE_UNSPEC)
>                         pfk->registered &= ~(1<<hdr->sadb_msg_satype);
> --
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- 
Gabriel Ryan
PhD Candidate at Columbia University
cs.columbia.edu/~gabe