2020-02-19 10:17:26

by Amol Grover

Subject: [PATCH] netfilter: ipt_CLUSTERIP: Pass lockdep expression to RCU lists

cn->configs is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of cn->lock.

Hence, add corresponding lockdep expression to silence false-positive
warnings, and harden RCU lists.

Signed-off-by: Amol Grover <[email protected]>
---
net/ipv4/netfilter/ipt_CLUSTERIP.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 6bdb1ab8af61..df856ff835b7 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -139,7 +139,8 @@ __clusterip_config_find(struct net *net, __be32 clusterip)
struct clusterip_config *c;
struct clusterip_net *cn = clusterip_pernet(net);

- list_for_each_entry_rcu(c, &cn->configs, list) {
+ list_for_each_entry_rcu(c, &cn->configs, list,
+ lockdep_is_held(&cn->lock)) {
if (c->clusterip == clusterip)
return c;
}
@@ -194,7 +195,8 @@ clusterip_netdev_event(struct notifier_block *this, unsigned long event,
struct clusterip_config *c;

spin_lock_bh(&cn->lock);
- list_for_each_entry_rcu(c, &cn->configs, list) {
+ list_for_each_entry_rcu(c, &cn->configs, list,
+ lockdep_is_held(&cn->lock)) {
switch (event) {
case NETDEV_REGISTER:
if (!strcmp(dev->name, c->ifname)) {
--
2.24.1

2020-03-02 12:37:48

by Pablo Neira Ayuso

Subject: Re: [PATCH] netfilter: ipt_CLUSTERIP: Pass lockdep expression to RCU lists

On Wed, Feb 19, 2020 at 03:46:27PM +0530, Amol Grover wrote:
> cn->configs is traversed using list_for_each_entry_rcu
> outside an RCU read-side critical section but under the protection
> of cn->lock.
>
> Hence, add corresponding lockdep expression to silence false-positive
> warnings, and harden RCU lists.
>
> Signed-off-by: Amol Grover <[email protected]>
> ---
> net/ipv4/netfilter/ipt_CLUSTERIP.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> index 6bdb1ab8af61..df856ff835b7 100644
> --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
> +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> @@ -139,7 +139,8 @@ __clusterip_config_find(struct net *net, __be32 clusterip)
> struct clusterip_config *c;
> struct clusterip_net *cn = clusterip_pernet(net);
>
> - list_for_each_entry_rcu(c, &cn->configs, list) {
> + list_for_each_entry_rcu(c, &cn->configs, list,
> + lockdep_is_held(&cn->lock)) {

bh is disabled before calling __clusterip_config_find(), then
rcu_read_lock_any_held() evaluates true.

Are you sure this really results in a WARN_ON splat?