| Message ID | 1406648188-3681-2-git-send-email-pablo@netfilter.org |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tue, Jul 29, 2014 at 8:36 AM, Pablo Neira Ayuso <pablo@netfilter.org> wrote: > sk_unattached_filter_destroy() does not always need to release the > filter object via rcu. Since this filter is never attached to the > socket, the caller should be responsible for releasing the filter > in a safe way, which may not necessarily imply rcu. > > This is a short summary of clients of this function: > > 1) xt_bpf.c and cls_bpf.c use the bpf matchers from rules, these rules > are removed from the packet path before the filter is released. Thus, > the framework makes sure the filter is safely removed. > > 2) In the ppp driver, the ppp_lock ensures serialization between the > xmit and filter attachment/detachment path. This doesn't use rcu > so deferred release via rcu makes no sense. > > 3) In the isdn/ppp driver, it is called from isdn_ppp_release() > the isdn_ppp_ioctl(). This driver uses mutex and spinlocks, no rcu. > Thus, deferred rcu makes no sense to me either, the deferred releases > may be just masking the effects of wrong locking strategy, which > should be fixed in the driver itself. > > 4) In the team driver, this is the only place where the rcu > synchronization with unattached filter is used. Therefore, this > patch introduces synchronize_rcu() which is called from the > genetlink path to make sure the filter doesn't go away while packets > are still walking over it. I think we can revisit this once struct > bpf_prog (that only wraps specific bpf code bits) is in place, then > add some specific struct rcu_head in the scope of the team driver if > Jiri thinks this is needed. Correct. There are also: 5) ptp_classifer - which is ok as well, since there is no filter_destroy. 6) seccomp - there I think it's also ok, since filter is called from syscall and filter freeing is done on task exit -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Pablo Neira Ayuso <pablo@netfilter.org> Date: Tue, 29 Jul 2014 17:36:28 +0200 > sk_unattached_filter_destroy() does not always need to release the > filter object via rcu. Since this filter is never attached to the > socket, the caller should be responsible for releasing the filter > in a safe way, which may not necessarily imply rcu. > > This is a short summary of clients of this function: > > 1) xt_bpf.c and cls_bpf.c use the bpf matchers from rules, these rules > are removed from the packet path before the filter is released. Thus, > the framework makes sure the filter is safely removed. > > 2) In the ppp driver, the ppp_lock ensures serialization between the > xmit and filter attachment/detachment path. This doesn't use rcu > so deferred release via rcu makes no sense. > > 3) In the isdn/ppp driver, it is called from isdn_ppp_release() > the isdn_ppp_ioctl(). This driver uses mutex and spinlocks, no rcu. > Thus, deferred rcu makes no sense to me either, the deferred releases > may be just masking the effects of wrong locking strategy, which > should be fixed in the driver itself. > > 4) In the team driver, this is the only place where the rcu > synchronization with unattached filter is used. Therefore, this > patch introduces synchronize_rcu() which is called from the > genetlink path to make sure the filter doesn't go away while packets > are still walking over it. I think we can revisit this once struct > bpf_prog (that only wraps specific bpf code bits) is in place, then > add some specific struct rcu_head in the scope of the team driver if > Jiri thinks this is needed. > > Deferred rcu release for unattached filters was originally introduced > in 302d663 ("filter: Allow to create sk-unattached filters"). > > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Also applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/team/team_mode_loadbalance.c b/drivers/net/team/team_mode_loadbalance.c index a58dfeb..7106f34 100644 --- a/drivers/net/team/team_mode_loadbalance.c +++ b/drivers/net/team/team_mode_loadbalance.c @@ -293,11 +293,15 @@ static int lb_bpf_func_set(struct team *team, struct team_gsetter_ctx *ctx) __fprog_destroy(lb_priv->ex->orig_fprog); orig_fp = rcu_dereference_protected(lb_priv->fp, lockdep_is_held(&team->lock)); - sk_unattached_filter_destroy(orig_fp); } rcu_assign_pointer(lb_priv->fp, fp); lb_priv->ex->orig_fprog = fprog; + + if (orig_fp) { + synchronize_rcu(); + sk_unattached_filter_destroy(orig_fp); + } return 0; } diff --git a/net/core/filter.c b/net/core/filter.c index f3b2d5e..42c1944 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -841,6 +841,12 @@ static void sk_release_orig_filter(struct sk_filter *fp) } } +static void __sk_filter_release(struct sk_filter *fp) +{ + sk_release_orig_filter(fp); + sk_filter_free(fp); +} + /** * sk_filter_release_rcu - Release a socket filter by rcu_head * @rcu: rcu_head that contains the sk_filter to free @@ -849,8 +855,7 @@ static void sk_filter_release_rcu(struct rcu_head *rcu) { struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu); - sk_release_orig_filter(fp); - sk_filter_free(fp); + __sk_filter_release(fp); } /** @@ -1050,7 +1055,7 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_create); void sk_unattached_filter_destroy(struct sk_filter *fp) { - sk_filter_release(fp); + __sk_filter_release(fp); } EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
sk_unattached_filter_destroy() does not always need to release the filter object via rcu. Since this filter is never attached to the socket, the caller should be responsible for releasing the filter in a safe way, which may not necessarily imply rcu. This is a short summary of clients of this function: 1) xt_bpf.c and cls_bpf.c use the bpf matchers from rules, these rules are removed from the packet path before the filter is released. Thus, the framework makes sure the filter is safely removed. 2) In the ppp driver, the ppp_lock ensures serialization between the xmit and filter attachment/detachment path. This doesn't use rcu so deferred release via rcu makes no sense. 3) In the isdn/ppp driver, it is called from isdn_ppp_release() the isdn_ppp_ioctl(). This driver uses mutex and spinlocks, no rcu. Thus, deferred rcu makes no sense to me either, the deferred releases may be just masking the effects of wrong locking strategy, which should be fixed in the driver itself. 4) In the team driver, this is the only place where the rcu synchronization with unattached filter is used. Therefore, this patch introduces synchronize_rcu() which is called from the genetlink path to make sure the filter doesn't go away while packets are still walking over it. I think we can revisit this once struct bpf_prog (that only wraps specific bpf code bits) is in place, then add some specific struct rcu_head in the scope of the team driver if Jiri thinks this is needed. Deferred rcu release for unattached filters was originally introduced in 302d663 ("filter: Allow to create sk-unattached filters"). Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> --- drivers/net/team/team_mode_loadbalance.c | 6 +++++- net/core/filter.c | 11 ++++++++--- 2 files changed, 13 insertions(+), 4 deletions(-)