af_key: Do not call xfrm_probe_algs in parallel

[PATCH] af_key: Do not call xfrm_probe_algs in parallel

Posted by Herbert Xu 3 years, 8 months ago

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

Re: [PATCH] af_key: Do not call xfrm_probe_algs in parallel

Posted by Gabriel Ryan 3 years, 7 months ago

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

Re: [PATCH] af_key: Do not call xfrm_probe_algs in parallel

Posted by Steffen Klassert 3 years, 8 months ago

On Thu, Aug 04, 2022 at 06:03:46PM +0800, Herbert Xu 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>

Applied, thanks a lot Herbert!