2019-03-05 01:21:48

by Su, Yanjun

Subject: [PATCH v2] net: xfrm: Add '_rcu' tag for rcu protected pointer in netns_xfrm

For rcu protected pointers, we'd better add '__rcu' for them.

Once added '__rcu' tag for rcu protected pointer, the sparse tool reports
warnings.

net/xfrm/xfrm_user.c:1198:39: sparse: expected struct sock *sk
net/xfrm/xfrm_user.c:1198:39: sparse: got struct sock [noderef] <asn:4> *nlsk
[...]

So introduce a new wrapper function of nlmsg_unicast to handle type
conversions.

No functional change.

Signed-off-by: Su Yanjun <[email protected]>
---
Changes from v1:
- fix spelling mistakes and the sparse tool' warnings

include/net/netns/xfrm.h | 2 +-
net/xfrm/xfrm_user.c | 30 +++++++++++++++++++++++-------
2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index 59f45b1..d2a36fb 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -57,7 +57,7 @@ struct netns_xfrm {
struct list_head inexact_bins;


- struct sock *nlsk;
+ struct sock __rcu *nlsk;
struct sock *nlsk_stash;

u32 sysctl_aevent_etime;
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index d832783..e8f23e4 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1071,6 +1071,22 @@ static inline int xfrm_nlmsg_multicast(struct net *net, struct sk_buff *skb,
return nlmsg_multicast(nlsk, skb, pid, group, GFP_ATOMIC);
}

+/* A similar wrapper like xfrm_nlmsg_multicast checking that nlsk is still
+ * available.
+ */
+static inline int xfrm_nlmsg_unicast(struct net *net, struct sk_buff *skb,
+ u32 pid)
+{
+ struct sock *nlsk = rcu_dereference(net->xfrm.nlsk);
+
+ if (!nlsk) {
+ kfree_skb(skb);
+ return -EPIPE;
+ }
+
+ return nlmsg_unicast(nlsk, skb, pid);
+}
+
static inline unsigned int xfrm_spdinfo_msgsize(void)
{
return NLMSG_ALIGN(4)
@@ -1195,7 +1211,7 @@ static int xfrm_get_spdinfo(struct sk_buff *skb, struct nlmsghdr *nlh,
err = build_spdinfo(r_skb, net, sportid, seq, *flags);
BUG_ON(err < 0);

- return nlmsg_unicast(net->xfrm.nlsk, r_skb, sportid);
+ return xfrm_nlmsg_unicast(net, r_skb, sportid);
}

static inline unsigned int xfrm_sadinfo_msgsize(void)
@@ -1254,7 +1270,7 @@ static int xfrm_get_sadinfo(struct sk_buff *skb, struct nlmsghdr *nlh,
err = build_sadinfo(r_skb, net, sportid, seq, *flags);
BUG_ON(err < 0);

- return nlmsg_unicast(net->xfrm.nlsk, r_skb, sportid);
+ return xfrm_nlmsg_unicast(net, r_skb, sportid);
}

static int xfrm_get_sa(struct sk_buff *skb, struct nlmsghdr *nlh,
@@ -1274,7 +1290,7 @@ static int xfrm_get_sa(struct sk_buff *skb, struct nlmsghdr *nlh,
if (IS_ERR(resp_skb)) {
err = PTR_ERR(resp_skb);
} else {
- err = nlmsg_unicast(net->xfrm.nlsk, resp_skb, NETLINK_CB(skb).portid);
+ err = xfrm_nlmsg_unicast(net, resp_skb, NETLINK_CB(skb).portid);
}
xfrm_state_put(x);
out_noput:
@@ -1337,7 +1353,7 @@ static int xfrm_alloc_userspi(struct sk_buff *skb, struct nlmsghdr *nlh,
goto out;
}

- err = nlmsg_unicast(net->xfrm.nlsk, resp_skb, NETLINK_CB(skb).portid);
+ err = xfrm_nlmsg_unicast(net, resp_skb, NETLINK_CB(skb).portid);

out:
xfrm_state_put(x);
@@ -1903,8 +1919,8 @@ static int xfrm_get_policy(struct sk_buff *skb, struct nlmsghdr *nlh,
if (IS_ERR(resp_skb)) {
err = PTR_ERR(resp_skb);
} else {
- err = nlmsg_unicast(net->xfrm.nlsk, resp_skb,
- NETLINK_CB(skb).portid);
+ err = xfrm_nlmsg_unicast(net, resp_skb,
+ NETLINK_CB(skb).portid);
}
} else {
xfrm_audit_policy_delete(xp, err ? 0 : 1, true);
@@ -2062,7 +2078,7 @@ static int xfrm_get_ae(struct sk_buff *skb, struct nlmsghdr *nlh,
err = build_aevent(r_skb, x, &c);
BUG_ON(err < 0);

- err = nlmsg_unicast(net->xfrm.nlsk, r_skb, NETLINK_CB(skb).portid);
+ err = xfrm_nlmsg_unicast(net, r_skb, NETLINK_CB(skb).portid);
spin_unlock_bh(&x->lock);
xfrm_state_put(x);
return err;
--
2.7.4

2019-03-06 13:34:06

by Steffen Klassert

Subject: Re: [PATCH v2] net: xfrm: Add '_rcu' tag for rcu protected pointer in netns_xfrm

On Mon, Mar 04, 2019 at 08:19:14PM -0500, Su Yanjun wrote:
> For rcu protected pointers, we'd better add '__rcu' for them.
>
> Once added '__rcu' tag for rcu protected pointer, the sparse tool reports
> warnings.
>
> net/xfrm/xfrm_user.c:1198:39: sparse: expected struct sock *sk
> net/xfrm/xfrm_user.c:1198:39: sparse: got struct sock [noderef] <asn:4> *nlsk
> [...]
>
> So introduce a new wrapper function of nlmsg_unicast to handle type
> conversions.
>
> No functional change.

While that was true for v1 of that patch, it is not
true for this version. This fixes a direct access
of a rcu protected socket. So please add a proper
'Fixes' tag.