Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Tue, Oct 24, 2017 at 9:25 PM, Steffen Klassert wrote: > On Tue, Oct 24, 2017 at 09:58:48AM -0700, Jonathan Basseri 😶 wrote: >> On Tue, Oct 24, 2017 at 12:04 AM, Steffen Klassert >> wrote: >> > >> > On Mon, Oct 23, 2017 at 06:18:55PM -0700, Jonathan Basseri wrote: >> > > If a socket has a valid dst cache, then xfrm_lookup_route will get >> > > skipped. However, the cache is not invalidated when applying policy to a >> > > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are >> > > sometimes ignored on those sockets. (Note: This was broken for IPv4 and >> > > IPv6 at different times.) >> > > >> > > This can be demonstrated like so, >> > > 1. Create UDP socket. >> > > 2. connect() the socket. >> > > 3. Apply an outbound XFRM policy to the socket. >> > > 4. send() data on the socket. >> > > >> > > Packets will continue to be sent in the clear instead of matching an >> > > xfrm or returning a no-match error (EAGAIN). This affects calls to >> > > send() and not sendto(). >> > > >> > > Invalidating the sk_dst_cache is necessary to correctly apply xfrm >> > > policies. Since we do this in xfrm_user_policy(), the sk_lock was >> > > already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(), >> > > and we may call __sk_dst_reset(). >> > > >> > > Performance impact should be negligible, since this code is only called >> > > when changing xfrm policy, and only affects the socket in question. >> > > >> > > Note: Creating normal XFRM policies should have a similar effect on >> > > sk_dst_cache entries that match the policy, but that is not fixed in >> > > this patch. >> > >> > I think we don't have this problem with 'normal' policies. When >> > inserting such a policy, we bump the IPv4/IPv6 genid. This should >> > invalidate all cached dst entries, no? >> > >> That sounds reasonable to me. I had not confirmed the behavior for >> normal policies, so I was trying to point out that this fix is only >> for socket policies. Should I modify the commit message? > > Yes, please do so. This comment may lead people to the wrong direction. > > Thanks! Thank you for the feedback. Sending a v2 patch with updated message.
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Tue, Oct 24, 2017 at 09:58:48AM -0700, Jonathan Basseri 😶 wrote: > On Tue, Oct 24, 2017 at 12:04 AM, Steffen Klassert > wrote: > > > > On Mon, Oct 23, 2017 at 06:18:55PM -0700, Jonathan Basseri wrote: > > > If a socket has a valid dst cache, then xfrm_lookup_route will get > > > skipped. However, the cache is not invalidated when applying policy to a > > > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are > > > sometimes ignored on those sockets. (Note: This was broken for IPv4 and > > > IPv6 at different times.) > > > > > > This can be demonstrated like so, > > > 1. Create UDP socket. > > > 2. connect() the socket. > > > 3. Apply an outbound XFRM policy to the socket. > > > 4. send() data on the socket. > > > > > > Packets will continue to be sent in the clear instead of matching an > > > xfrm or returning a no-match error (EAGAIN). This affects calls to > > > send() and not sendto(). > > > > > > Invalidating the sk_dst_cache is necessary to correctly apply xfrm > > > policies. Since we do this in xfrm_user_policy(), the sk_lock was > > > already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(), > > > and we may call __sk_dst_reset(). > > > > > > Performance impact should be negligible, since this code is only called > > > when changing xfrm policy, and only affects the socket in question. > > > > > > Note: Creating normal XFRM policies should have a similar effect on > > > sk_dst_cache entries that match the policy, but that is not fixed in > > > this patch. > > > > I think we don't have this problem with 'normal' policies. When > > inserting such a policy, we bump the IPv4/IPv6 genid. This should > > invalidate all cached dst entries, no? > > > That sounds reasonable to me. I had not confirmed the behavior for > normal policies, so I was trying to point out that this fix is only > for socket policies. Should I modify the commit message? Yes, please do so. This comment may lead people to the wrong direction. Thanks!
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Tue, Oct 24, 2017 at 12:04 AM, Steffen Klassert wrote: > > On Mon, Oct 23, 2017 at 06:18:55PM -0700, Jonathan Basseri wrote: > > If a socket has a valid dst cache, then xfrm_lookup_route will get > > skipped. However, the cache is not invalidated when applying policy to a > > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are > > sometimes ignored on those sockets. (Note: This was broken for IPv4 and > > IPv6 at different times.) > > > > This can be demonstrated like so, > > 1. Create UDP socket. > > 2. connect() the socket. > > 3. Apply an outbound XFRM policy to the socket. > > 4. send() data on the socket. > > > > Packets will continue to be sent in the clear instead of matching an > > xfrm or returning a no-match error (EAGAIN). This affects calls to > > send() and not sendto(). > > > > Invalidating the sk_dst_cache is necessary to correctly apply xfrm > > policies. Since we do this in xfrm_user_policy(), the sk_lock was > > already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(), > > and we may call __sk_dst_reset(). > > > > Performance impact should be negligible, since this code is only called > > when changing xfrm policy, and only affects the socket in question. > > > > Note: Creating normal XFRM policies should have a similar effect on > > sk_dst_cache entries that match the policy, but that is not fixed in > > this patch. > > I think we don't have this problem with 'normal' policies. When > inserting such a policy, we bump the IPv4/IPv6 genid. This should > invalidate all cached dst entries, no? > That sounds reasonable to me. I had not confirmed the behavior for normal policies, so I was trying to point out that this fix is only for socket policies. Should I modify the commit message?
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Mon, Oct 23, 2017 at 06:18:55PM -0700, Jonathan Basseri wrote: > If a socket has a valid dst cache, then xfrm_lookup_route will get > skipped. However, the cache is not invalidated when applying policy to a > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are > sometimes ignored on those sockets. (Note: This was broken for IPv4 and > IPv6 at different times.) > > This can be demonstrated like so, > 1. Create UDP socket. > 2. connect() the socket. > 3. Apply an outbound XFRM policy to the socket. > 4. send() data on the socket. > > Packets will continue to be sent in the clear instead of matching an > xfrm or returning a no-match error (EAGAIN). This affects calls to > send() and not sendto(). > > Invalidating the sk_dst_cache is necessary to correctly apply xfrm > policies. Since we do this in xfrm_user_policy(), the sk_lock was > already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(), > and we may call __sk_dst_reset(). > > Performance impact should be negligible, since this code is only called > when changing xfrm policy, and only affects the socket in question. > > Note: Creating normal XFRM policies should have a similar effect on > sk_dst_cache entries that match the policy, but that is not fixed in > this patch. I think we don't have this problem with 'normal' policies. When inserting such a policy, we bump the IPv4/IPv6 genid. This should invalidate all cached dst entries, no?
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Mon, Oct 23, 2017 at 6:18 PM, Jonathan Basseri
wrote:
> If a socket has a valid dst cache, then xfrm_lookup_route will get
> skipped. However, the cache is not invalidated when applying policy to a
> socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are
> sometimes ignored on those sockets. (Note: This was broken for IPv4 and
> IPv6 at different times.)
>
> This can be demonstrated like so,
> 1. Create UDP socket.
> 2. connect() the socket.
> 3. Apply an outbound XFRM policy to the socket.
> 4. send() data on the socket.
>
> Packets will continue to be sent in the clear instead of matching an
> xfrm or returning a no-match error (EAGAIN). This affects calls to
> send() and not sendto().
>
> Invalidating the sk_dst_cache is necessary to correctly apply xfrm
> policies. Since we do this in xfrm_user_policy(), the sk_lock was
> already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(),
> and we may call __sk_dst_reset().
>
> Performance impact should be negligible, since this code is only called
> when changing xfrm policy, and only affects the socket in question.
>
> Note: Creating normal XFRM policies should have a similar effect on
> sk_dst_cache entries that match the policy, but that is not fixed in
> this patch.
>
> Fixes: 00bc0ef5880d ("ipv6: Skip XFRM lookup if dst_entry in socket cache is
> valid")
> Tested: https://android-review.googlesource.com/517555
> Tested: https://android-review.googlesource.com/418659
> Signed-off-by: Jonathan Basseri
>
> diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
> index 12213477cd3a..1f5cee2269af 100644
> --- a/net/xfrm/xfrm_state.c
> +++ b/net/xfrm/xfrm_state.c
> @@ -2045,33 +2045,34 @@ EXPORT_SYMBOL(km_is_alive);
> int xfrm_user_policy(struct sock *sk, int optname, u8 __user *optval, int
> optlen)
> {
> int err;
> u8 *data;
> struct xfrm_mgr *km;
> struct xfrm_policy *pol = NULL;
>
> if (optlen <= 0 || optlen > PAGE_SIZE)
> return -EMSGSIZE;
>
> data = memdup_user(optval, optlen);
> if (IS_ERR(data))
> return PTR_ERR(data);
>
> err = -EINVAL;
> rcu_read_lock();
> list_for_each_entry_rcu(km, &xfrm_km_list, list) {
> pol = km->compile_policy(sk, optname, data,
> optlen, &err);
> if (err >= 0)
> break;
> }
> rcu_read_unlock();
>
> if (err >= 0) {
> xfrm_sk_policy_insert(sk, err, pol);
> xfrm_pol_put(pol);
> + __sk_dst_reset(sk);
> err = 0;
> }
>
> kfree(data);
> return err;
> }
> --
> 2.15.0.rc0.271.g36b669edcc-goog
>
I discussed the concerns with Eric and I believe this addresses them.
(http://www.spinics.net/lists/netdev/msg449652.html)
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Wed, 16 Aug 2017 03:43:54 -0700
Eric Dumazet wrote:
> On Wed, 2017-08-16 at 11:03 +0200, Jakub Sitnicki wrote:
> > On Tue, 15 Aug 2017 15:25:10 -0700
> > Jonathan Basseri wrote:
> >
> > > If an IPv6 socket has a valid dst cache, then xfrm_lookup_route will get
> > > skipped. However, the cache is not invalidated when applying policy to a
> > > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are
> > > sometimes ignored on those sockets.
> > >
> > > This can be demonstrated like so,
> > > 1. Create UDPv6 socket.
> > > 2. connect() the socket.
> > > 3. Apply an outbound XFRM policy to the socket.
> > > 4. send() data on the socket.
> > >
> > > Packets will continue to be sent in the clear instead of matching an
> > > xfrm or returning a no-match error (EAGAIN). This affects calls to
> > > send() and not sendto().
> > >
> > > Note: Creating normal XFRM policies should have a similar effect on
> > > sk_dst_cache entries that match the policy, but that is not fixed in
> > > this patch.
> > >
> > > Fixes: 00bc0ef5880d ("ipv6: Skip XFRM lookup if dst_entry in socket cache
> > > is valid")
> > > Tested: https://android-review.googlesource.com/418659
> > > Signed-off-by: Jonathan Basseri
> > > ---
> >
> > Thank you for the fix.
> >
> > Acked-by: Jakub Sitnicki
>
> I do not believe this fix is correct.
>
> What happens if the socket is TCP ?
>
> sk_dst_reset(sk) is not safe for them.
>
> This might add use-after-free, and eventually crash.
You are right. I see that RCU-variant __sk_dst_reset() is used
throughout TCP stack. Thank you for pointing it out.
Please disregard my earlier ACK.
-Jakub
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Wed, 2017-08-16 at 11:03 +0200, Jakub Sitnicki wrote:
> On Tue, 15 Aug 2017 15:25:10 -0700
> Jonathan Basseri wrote:
>
> > If an IPv6 socket has a valid dst cache, then xfrm_lookup_route will get
> > skipped. However, the cache is not invalidated when applying policy to a
> > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are
> > sometimes ignored on those sockets.
> >
> > This can be demonstrated like so,
> > 1. Create UDPv6 socket.
> > 2. connect() the socket.
> > 3. Apply an outbound XFRM policy to the socket.
> > 4. send() data on the socket.
> >
> > Packets will continue to be sent in the clear instead of matching an
> > xfrm or returning a no-match error (EAGAIN). This affects calls to
> > send() and not sendto().
> >
> > Note: Creating normal XFRM policies should have a similar effect on
> > sk_dst_cache entries that match the policy, but that is not fixed in
> > this patch.
> >
> > Fixes: 00bc0ef5880d ("ipv6: Skip XFRM lookup if dst_entry in socket cache
> > is valid")
> > Tested: https://android-review.googlesource.com/418659
> > Signed-off-by: Jonathan Basseri
> > ---
>
> Thank you for the fix.
>
> Acked-by: Jakub Sitnicki
I do not believe this fix is correct.
What happens if the socket is TCP ?
sk_dst_reset(sk) is not safe for them.
This might add use-after-free, and eventually crash.
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Tue, 15 Aug 2017 15:25:10 -0700
Jonathan Basseri wrote:
> If an IPv6 socket has a valid dst cache, then xfrm_lookup_route will get
> skipped. However, the cache is not invalidated when applying policy to a
> socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are
> sometimes ignored on those sockets.
>
> This can be demonstrated like so,
> 1. Create UDPv6 socket.
> 2. connect() the socket.
> 3. Apply an outbound XFRM policy to the socket.
> 4. send() data on the socket.
>
> Packets will continue to be sent in the clear instead of matching an
> xfrm or returning a no-match error (EAGAIN). This affects calls to
> send() and not sendto().
>
> Note: Creating normal XFRM policies should have a similar effect on
> sk_dst_cache entries that match the policy, but that is not fixed in
> this patch.
>
> Fixes: 00bc0ef5880d ("ipv6: Skip XFRM lookup if dst_entry in socket cache is
> valid")
> Tested: https://android-review.googlesource.com/418659
> Signed-off-by: Jonathan Basseri
> ---
Thank you for the fix.
Acked-by: Jakub Sitnicki
Re: [PATCH net] xfrm: Clear sk_dst_cache when applying per-socket policy.
On Wed, Aug 16, 2017 at 7:25 AM, Jonathan Basseri wrote: > If an IPv6 socket has a valid dst cache Did you look into why IPv4 does not suffer from this problem? That said, clearing the dst cache entry does seem prudent in general.
