diff mbox series

[net-next,RFC,1/2] net: devlink: make sure that devlink_try_get() works with valid pointer during xarray iteration

Message ID 20220627135501.713980-2-jiri@resnulli.us (mailing list archive)
State RFC
Delegated to: Netdev Maintainers
Headers show
Series net: devlink: remove devlink big lock | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit fail Errors and warnings before: 2 this patch: 3
netdev/cc_maintainers warning 1 maintainers not CCed: jiri@nvidia.com
netdev/build_clang success Errors and warnings before: 6 this patch: 6
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn fail Errors and warnings before: 2 this patch: 3
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 447 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Jiri Pirko June 27, 2022, 1:55 p.m. UTC 
From: Jiri Pirko <jiri@nvidia.com>

Remove dependency on devlink_mutex during devlinks xarray iteration.

The devlinks xarray consistency is ensured by internally by xarray.
There is a reference taken when working with devlink using
devlink_try_get(). But there is no guarantee that devlink pointer
picked during xarray iteration is not freed before devlink_try_get()
is called.

Make sure that devlink_try_get() works with valid pointer.
Achieve it by:
1) Splitting devlink_put() so the completion is sent only
   after grace period. Completion unblocks the devlink_unregister()
   routine, which is followed-up by devlink_free()
2) Iterate the devlink xarray holding RCU read lock.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
 net/core/devlink.c | 113 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 95 insertions(+), 18 deletions(-)
diff mbox series

Patch

diff --git a/net/core/devlink.c b/net/core/devlink.c
index db61f3a341cb..9e34b4b9b19b 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -69,6 +69,7 @@  struct devlink {
 	u8 reload_failed:1;
 	refcount_t refcount;
 	struct completion comp;
+	struct rcu_head rcu;
 	char priv[] __aligned(NETDEV_ALIGN);
 };
 
@@ -220,8 +221,6 @@  static DEFINE_XARRAY_FLAGS(devlinks, XA_FLAGS_ALLOC);
 /* devlink_mutex
  *
  * An overall lock guarding every operation coming from userspace.
- * It also guards devlink devices list and it is taken when
- * driver registers/unregisters it.
  */
 static DEFINE_MUTEX(devlink_mutex);
 
@@ -231,10 +230,21 @@  struct net *devlink_net(const struct devlink *devlink)
 }
 EXPORT_SYMBOL_GPL(devlink_net);
 
+static void __devlink_put_rcu(struct rcu_head *head)
+{
+	struct devlink *devlink = container_of(head, struct devlink, rcu);
+
+	complete(&devlink->comp);
+}
+
 void devlink_put(struct devlink *devlink)
 {
 	if (refcount_dec_and_test(&devlink->refcount))
-		complete(&devlink->comp);
+		/* Make sure unregister operation that may await the completion
+		 * is unblocked only after all users are after the enf of
+		 * RCU grace period.
+		 */
+		call_rcu(&devlink->rcu, __devlink_put_rcu);
 }
 
 struct devlink *__must_check devlink_try_get(struct devlink *devlink)
@@ -288,6 +298,7 @@  static struct devlink *devlink_get_from_attrs(struct net *net,
 
 	lockdep_assert_held(&devlink_mutex);
 
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (strcmp(devlink->dev->bus->name, busname) == 0 &&
 		    strcmp(dev_name(devlink->dev), devname) == 0 &&
@@ -299,6 +310,7 @@  static struct devlink *devlink_get_from_attrs(struct net *net,
 
 	if (!found || !devlink_try_get(devlink))
 		devlink = ERR_PTR(-ENODEV);
+	rcu_read_unlock();
 
 	return devlink;
 }
@@ -1322,9 +1334,11 @@  static int devlink_nl_cmd_rate_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -1351,7 +1365,9 @@  static int devlink_nl_cmd_rate_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 	if (err != -EMSGSIZE)
@@ -1425,29 +1441,32 @@  static int devlink_nl_cmd_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
-		if (!net_eq(devlink_net(devlink), sock_net(msg->sk))) {
-			devlink_put(devlink);
-			continue;
-		}
+		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
+			goto retry;
 
-		if (idx < start) {
-			idx++;
-			devlink_put(devlink);
-			continue;
-		}
+		if (idx < start)
+			goto inc;
 
 		err = devlink_nl_fill(msg, devlink, DEVLINK_CMD_NEW,
 				      NETLINK_CB(cb->skb).portid,
 				      cb->nlh->nlmsg_seq, NLM_F_MULTI);
-		devlink_put(devlink);
-		if (err)
+		if (err) {
+			devlink_put(devlink);
 			goto out;
+		}
+inc:
 		idx++;
+retry:
+		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -1488,9 +1507,11 @@  static int devlink_nl_cmd_port_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -1516,7 +1537,9 @@  static int devlink_nl_cmd_port_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -2173,9 +2196,11 @@  static int devlink_nl_cmd_linecard_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -2204,7 +2229,9 @@  static int devlink_nl_cmd_linecard_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->linecards_lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -2445,9 +2472,11 @@  static int devlink_nl_cmd_sb_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -2473,7 +2502,9 @@  static int devlink_nl_cmd_sb_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -2597,9 +2628,11 @@  static int devlink_nl_cmd_sb_pool_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
 		    !devlink->ops->sb_pool_get)
@@ -2622,7 +2655,9 @@  static int devlink_nl_cmd_sb_pool_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -2818,9 +2853,11 @@  static int devlink_nl_cmd_sb_port_pool_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
 		    !devlink->ops->sb_port_pool_get)
@@ -2843,7 +2880,9 @@  static int devlink_nl_cmd_sb_port_pool_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -3067,9 +3106,11 @@  devlink_nl_cmd_sb_tc_pool_bind_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
 		    !devlink->ops->sb_tc_pool_bind_get)
@@ -3093,7 +3134,9 @@  devlink_nl_cmd_sb_tc_pool_bind_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -5154,9 +5197,11 @@  static int devlink_nl_cmd_param_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -5184,7 +5229,9 @@  static int devlink_nl_cmd_param_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -5389,9 +5436,11 @@  static int devlink_nl_cmd_port_param_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -5424,7 +5473,9 @@  static int devlink_nl_cmd_port_param_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -5973,9 +6024,11 @@  static int devlink_nl_cmd_region_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -5986,7 +6039,9 @@  static int devlink_nl_cmd_region_get_dumpit(struct sk_buff *msg,
 		devlink_put(devlink);
 		if (err)
 			goto out;
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 	cb->args[0] = idx;
@@ -6507,9 +6562,11 @@  static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -6533,7 +6590,9 @@  static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
 		idx++;
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 	mutex_unlock(&devlink_mutex);
 
 	if (err != -EMSGSIZE)
@@ -7687,9 +7746,11 @@  devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry_rep;
@@ -7715,11 +7776,13 @@  devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->reporters_lock);
 retry_rep:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
 
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry_port;
@@ -7750,7 +7813,9 @@  devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry_port:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -8287,9 +8352,11 @@  static int devlink_nl_cmd_trap_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -8315,7 +8382,9 @@  static int devlink_nl_cmd_trap_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -8514,9 +8583,11 @@  static int devlink_nl_cmd_trap_group_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -8543,7 +8614,9 @@  static int devlink_nl_cmd_trap_group_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -8828,9 +8901,11 @@  static int devlink_nl_cmd_trap_policer_get_dumpit(struct sk_buff *msg,
 	int err;
 
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			goto retry;
@@ -8857,7 +8932,9 @@  static int devlink_nl_cmd_trap_policer_get_dumpit(struct sk_buff *msg,
 		mutex_unlock(&devlink->lock);
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 out:
 	mutex_unlock(&devlink_mutex);
 
@@ -9585,10 +9662,8 @@  void devlink_register(struct devlink *devlink)
 	ASSERT_DEVLINK_NOT_REGISTERED(devlink);
 	/* Make sure that we are in .probe() routine */
 
-	mutex_lock(&devlink_mutex);
 	xa_set_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
 	devlink_notify_register(devlink);
-	mutex_unlock(&devlink_mutex);
 }
 EXPORT_SYMBOL_GPL(devlink_register);
 
@@ -9605,10 +9680,8 @@  void devlink_unregister(struct devlink *devlink)
 	devlink_put(devlink);
 	wait_for_completion(&devlink->comp);
 
-	mutex_lock(&devlink_mutex);
 	devlink_notify_unregister(devlink);
 	xa_clear_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
-	mutex_unlock(&devlink_mutex);
 }
 EXPORT_SYMBOL_GPL(devlink_unregister);
 
@@ -12118,9 +12191,11 @@  static void __net_exit devlink_pernet_pre_exit(struct net *net)
 	 * all devlink instances from this namespace into init_net.
 	 */
 	mutex_lock(&devlink_mutex);
+	rcu_read_lock();
 	xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
 		if (!devlink_try_get(devlink))
 			continue;
+		rcu_read_unlock();
 
 		if (!net_eq(devlink_net(devlink), net))
 			goto retry;
@@ -12134,7 +12209,9 @@  static void __net_exit devlink_pernet_pre_exit(struct net *net)
 			pr_warn("Failed to reload devlink instance into init_net\n");
 retry:
 		devlink_put(devlink);
+		rcu_read_lock();
 	}
+	rcu_read_unlock();
 	mutex_unlock(&devlink_mutex);
 }