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Date: Sat, 4 Dec 2021 20:21:57 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH v3 net-next 03/23] net: add net device refcount tracker infrastructure
From: Eric Dumazet <edumazet@...gle.com>
net device are refcounted. Over the years we had numerous bugs
caused by imbalanced dev_hold() and dev_put() calls.
The general idea is to be able to precisely pair each decrement with
a corresponding prior increment. Both share a cookie, basically
a pointer to private data storing stack traces.
This patch adds dev_hold_track() and dev_put_track().
To use these helpers, each data structure owning a refcount
should also use a "netdevice_tracker" to pair the hold and put.
netdevice_tracker dev_tracker;
...
dev_hold_track(dev, &dev_tracker, GFP_ATOMIC);
...
dev_put_track(dev, &dev_tracker);
Whenever a leak happens, we will get precise stack traces
of the point dev_hold_track() happened, at device dismantle phase.
We will also get a stack trace if too many dev_put_track() for the same
netdevice_tracker are attempted.
This is guarded by CONFIG_NET_DEV_REFCNT_TRACKER option.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/netdevice.h | 45 +++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 5 +++++
net/Kconfig.debug | 11 ++++++++++
net/core/dev.c | 3 +++
4 files changed, 64 insertions(+)
create mode 100644 net/Kconfig.debug
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 65117f01d5f2a9c9e815b6c967d5e9e4c94af0ae..143d60ed004732e4a086e66fdcf7b3d362c1dc20 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -48,6 +48,7 @@
#include <uapi/linux/pkt_cls.h>
#include <linux/hashtable.h>
#include <linux/rbtree.h>
+#include <linux/ref_tracker.h>
struct netpoll_info;
struct device;
@@ -300,6 +301,12 @@ enum netdev_state_t {
};
+#ifdef CONFIG_NET_DEV_REFCNT_TRACKER
+typedef struct ref_tracker *netdevice_tracker;
+#else
+typedef struct {} netdevice_tracker;
+#endif
+
struct gro_list {
struct list_head list;
int count;
@@ -1865,6 +1872,7 @@ enum netdev_ml_priv_type {
* @proto_down_reason: reason a netdev interface is held down
* @pcpu_refcnt: Number of references to this device
* @dev_refcnt: Number of references to this device
+ * @refcnt_tracker: Tracker directory for tracked references to this device
* @todo_list: Delayed register/unregister
* @link_watch_list: XXX: need comments on this one
*
@@ -2178,6 +2186,7 @@ struct net_device {
#else
refcount_t dev_refcnt;
#endif
+ struct ref_tracker_dir refcnt_tracker;
struct list_head link_watch_list;
@@ -3805,6 +3814,7 @@ void netdev_run_todo(void);
* @dev: network device
*
* Release reference to device to allow it to be freed.
+ * Try using dev_put_track() instead.
*/
static inline void dev_put(struct net_device *dev)
{
@@ -3822,6 +3832,7 @@ static inline void dev_put(struct net_device *dev)
* @dev: network device
*
* Hold reference to device to keep it from being freed.
+ * Try using dev_hold_track() instead.
*/
static inline void dev_hold(struct net_device *dev)
{
@@ -3834,6 +3845,40 @@ static inline void dev_hold(struct net_device *dev)
}
}
+static inline void netdev_tracker_alloc(struct net_device *dev,
+ netdevice_tracker *tracker, gfp_t gfp)
+{
+#ifdef CONFIG_NET_DEV_REFCNT_TRACKER
+ ref_tracker_alloc(&dev->refcnt_tracker, tracker, gfp);
+#endif
+}
+
+static inline void netdev_tracker_free(struct net_device *dev,
+ netdevice_tracker *tracker)
+{
+#ifdef CONFIG_NET_DEV_REFCNT_TRACKER
+ ref_tracker_free(&dev->refcnt_tracker, tracker);
+#endif
+}
+
+static inline void dev_hold_track(struct net_device *dev,
+ netdevice_tracker *tracker, gfp_t gfp)
+{
+ if (dev) {
+ dev_hold(dev);
+ netdev_tracker_alloc(dev, tracker, gfp);
+ }
+}
+
+static inline void dev_put_track(struct net_device *dev,
+ netdevice_tracker *tracker)
+{
+ if (dev) {
+ netdev_tracker_free(dev, tracker);
+ dev_put(dev);
+ }
+}
+
/* Carrier loss detection, dial on demand. The functions netif_carrier_on
* and _off may be called from IRQ context, but it is caller
* who is responsible for serialization of these calls.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 633c2c5cb45bd435a7684dbe2f2eca477c871463..6504b97f8dfd786b6a7b9cdb2c2eda5aaa2c2b03 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -598,6 +598,11 @@ config DEBUG_MISC
Say Y here if you need to enable miscellaneous debug code that should
be under a more specific debug option but isn't.
+menu "Networking Debugging"
+
+source "net/Kconfig.debug"
+
+endmenu # "Networking Debugging"
menu "Memory Debugging"
diff --git a/net/Kconfig.debug b/net/Kconfig.debug
new file mode 100644
index 0000000000000000000000000000000000000000..ee8d67a784291fb126d95324db05183b5a78ab70
--- /dev/null
+++ b/net/Kconfig.debug
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config NET_DEV_REFCNT_TRACKER
+ bool "Enable net device refcount tracking"
+ depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
+ select REF_TRACKER
+ default n
+ help
+ Enable debugging feature to track device references.
+ This adds memory and cpu costs.
+
diff --git a/net/core/dev.c b/net/core/dev.c
index aba8acc1238c2213b9fc0c47c93568f731f375e5..1740d6cfe86b58359cceaec7ee9cc015a3843723 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9864,6 +9864,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
netdev_unregister_timeout_secs * HZ)) {
pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
dev->name, refcnt);
+ ref_tracker_dir_print(&dev->refcnt_tracker, 10);
warning_time = jiffies;
}
}
@@ -10154,6 +10155,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev = PTR_ALIGN(p, NETDEV_ALIGN);
dev->padded = (char *)dev - (char *)p;
+ ref_tracker_dir_init(&dev->refcnt_tracker, 128);
#ifdef CONFIG_PCPU_DEV_REFCNT
dev->pcpu_refcnt = alloc_percpu(int);
if (!dev->pcpu_refcnt)
@@ -10270,6 +10272,7 @@ void free_netdev(struct net_device *dev)
list_for_each_entry_safe(p, n, &dev->napi_list, dev_list)
netif_napi_del(p);
+ ref_tracker_dir_exit(&dev->refcnt_tracker);
#ifdef CONFIG_PCPU_DEV_REFCNT
free_percpu(dev->pcpu_refcnt);
dev->pcpu_refcnt = NULL;
--
2.34.1.400.ga245620fadb-goog
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