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rtnetlink: Protect struct rtnl_af_ops with SRCU.

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Once RTNL is replaced with rtnl_net_lock(), we need a mechanism to
guarantee that rtnl_af_ops is alive during inflight RTM_SETLINK
even when its module is being unloaded.

Let's use SRCU to protect ops.

rtnl_af_lookup() now iterates rtnl_af_ops under RCU and returns
SRCU-protected ops pointer.  The caller must call rtnl_af_put()
to release the pointer after the use.

Also, rtnl_af_unregister() unlinks the ops first and calls
synchronize_srcu() to wait for inflight RTM_SETLINK requests to
complete.

Note that rtnl_af_ops needs to be protected by its dedicated lock
when RTNL is removed.

Note also that BUG_ON() in do_setlink() is changed to the normal
error handling as a different af_ops might be found after
validate_linkmsg().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima
2024-10-16 11:53:57 -07:00
committed by Paolo Abeni
parent 26eebdc4b0
commit 6ab0f86694
2 changed files with 51 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
include/net/rtnetlink.h
View File

@@ -172,7 +172,8 @@ void rtnl_link_unregister(struct rtnl_link_ops *ops);
/**
* struct rtnl_af_ops - rtnetlink address family operations
*
* @list: Used internally
* @list: Used internally, protected by RTNL and SRCU
* @srcu: Used internally
* @family: Address family
* @fill_link_af: Function to fill IFLA_AF_SPEC with address family
* specific netlink attributes.
@@ -185,6 +186,8 @@ void rtnl_link_unregister(struct rtnl_link_ops *ops);
*/
struct rtnl_af_ops {
struct list_head list;
struct srcu_struct srcu;
int family;
int (*fill_link_af)(struct sk_buff *skb,

63
net/core/rtnetlink.c
View File

@@ -666,18 +666,31 @@ static size_t rtnl_link_get_size(const struct net_device *dev)
static LIST_HEAD(rtnl_af_ops);
static const struct rtnl_af_ops *rtnl_af_lookup(const int family)
static struct rtnl_af_ops *rtnl_af_lookup(const int family, int *srcu_index)
{
const struct rtnl_af_ops *ops;
struct rtnl_af_ops *ops;
ASSERT_RTNL();
list_for_each_entry(ops, &rtnl_af_ops, list) {
if (ops->family == family)
return ops;
rcu_read_lock();
list_for_each_entry_rcu(ops, &rtnl_af_ops, list) {
if (ops->family == family) {
*srcu_index = srcu_read_lock(&ops->srcu);
goto unlock;
}
}
return NULL;
ops = NULL;
unlock:
rcu_read_unlock();
return ops;
}
static void rtnl_af_put(struct rtnl_af_ops *ops, int srcu_index)
{
srcu_read_unlock(&ops->srcu, srcu_index);
}
/**
@@ -688,6 +701,11 @@ static const struct rtnl_af_ops *rtnl_af_lookup(const int family)
*/
int rtnl_af_register(struct rtnl_af_ops *ops)
{
int err = init_srcu_struct(&ops->srcu);
if (err)
return err;
rtnl_lock();
list_add_tail_rcu(&ops->list, &rtnl_af_ops);
rtnl_unlock();
@@ -707,6 +725,8 @@ void rtnl_af_unregister(struct rtnl_af_ops *ops)
rtnl_unlock();
synchronize_rcu();
synchronize_srcu(&ops->srcu);
cleanup_srcu_struct(&ops->srcu);
}
EXPORT_SYMBOL_GPL(rtnl_af_unregister);
@@ -2579,20 +2599,24 @@ static int validate_linkmsg(struct net_device *dev, struct nlattr *tb[],
int rem, err;
nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {
const struct rtnl_af_ops *af_ops;
struct rtnl_af_ops *af_ops;
int af_ops_srcu_index;
af_ops = rtnl_af_lookup(nla_type(af));
af_ops = rtnl_af_lookup(nla_type(af), &af_ops_srcu_index);
if (!af_ops)
return -EAFNOSUPPORT;
if (!af_ops->set_link_af)
return -EOPNOTSUPP;
if (af_ops->validate_link_af) {
err = -EOPNOTSUPP;
else if (af_ops->validate_link_af)
err = af_ops->validate_link_af(dev, af, extack);
if (err < 0)
return err;
}
else
err = 0;
rtnl_af_put(af_ops, af_ops_srcu_index);
if (err < 0)
return err;
}
}
@@ -3172,11 +3196,18 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
int rem;
nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {
const struct rtnl_af_ops *af_ops;
struct rtnl_af_ops *af_ops;
int af_ops_srcu_index;
BUG_ON(!(af_ops = rtnl_af_lookup(nla_type(af))));
af_ops = rtnl_af_lookup(nla_type(af), &af_ops_srcu_index);
if (!af_ops) {
err = -EAFNOSUPPORT;
goto errout;
}
err = af_ops->set_link_af(dev, af, extack);
rtnl_af_put(af_ops, af_ops_srcu_index);
if (err < 0)
goto errout;