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Message-Id: <20220204224237.2932026-4-eric.dumazet@gmail.com>
Date: Fri, 4 Feb 2022 14:42:37 -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>
Subject: [PATCH v2 net-next 3/3] net: refine dev_put()/dev_hold() debugging
From: Eric Dumazet <edumazet@...gle.com>
We are still chasing some syzbot reports where we think a rogue dev_put()
is called with no corresponding prior dev_hold().
Unfortunately it eats a reference on dev->dev_refcnt taken by innocent
dev_hold_track(), meaning that the refcount saturation splat comes
too late to be useful.
Make sure that 'not tracked' dev_put() and dev_hold() better use
CONFIG_NET_DEV_REFCNT_TRACKER=y debug infrastructure:
Prior patch in the series allowed ref_tracker_alloc() and ref_tracker_free()
to be called with a NULL @trackerp parameter, and to use a separate refcount
only to detect too many put() even in the following case:
dev_hold_track(dev, tracker_1, GFP_ATOMIC);
dev_hold(dev);
dev_put(dev);
dev_put(dev); // Should complain loudly here.
dev_put_track(dev, tracker_1); // instead of here
Add clarification about netdev_tracker_alloc() role.
v2: I replaced the dev_put() in linkwatch_do_dev()
with __dev_put() because callers called netdev_tracker_free().
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/netdevice.h | 69 ++++++++++++++++++++++++++-------------
net/core/dev.c | 2 +-
net/core/link_watch.c | 6 ++--
3 files changed, 50 insertions(+), 27 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e490b84732d1654bf067b30f2bb0b0825f88dea9..3fb6fb67ed77e70314a699c9bdf8f4b26acfcc19 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3817,14 +3817,7 @@ extern unsigned int netdev_budget_usecs;
/* Called by rtnetlink.c:rtnl_unlock() */
void netdev_run_todo(void);
-/**
- * dev_put - release reference to device
- * @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)
+static inline void __dev_put(struct net_device *dev)
{
if (dev) {
#ifdef CONFIG_PCPU_DEV_REFCNT
@@ -3835,14 +3828,7 @@ static inline void dev_put(struct net_device *dev)
}
}
-/**
- * dev_hold - get reference to device
- * @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)
+static inline void __dev_hold(struct net_device *dev)
{
if (dev) {
#ifdef CONFIG_PCPU_DEV_REFCNT
@@ -3853,11 +3839,24 @@ 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
+}
+
+/* netdev_tracker_alloc() can upgrade a prior untracked reference
+ * taken by dev_get_by_name()/dev_get_by_index() to a tracked one.
+ */
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);
+ refcount_dec(&dev->refcnt_tracker.no_tracker);
+ __netdev_tracker_alloc(dev, tracker, gfp);
#endif
}
@@ -3873,8 +3872,8 @@ 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);
+ __dev_hold(dev);
+ __netdev_tracker_alloc(dev, tracker, gfp);
}
}
@@ -3883,10 +3882,34 @@ static inline void dev_put_track(struct net_device *dev,
{
if (dev) {
netdev_tracker_free(dev, tracker);
- dev_put(dev);
+ __dev_put(dev);
}
}
+/**
+ * dev_hold - get reference to device
+ * @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)
+{
+ dev_hold_track(dev, NULL, GFP_ATOMIC);
+}
+
+/**
+ * dev_put - release reference to device
+ * @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)
+{
+ dev_put_track(dev, NULL);
+}
+
static inline void dev_replace_track(struct net_device *odev,
struct net_device *ndev,
netdevice_tracker *tracker,
@@ -3895,11 +3918,11 @@ static inline void dev_replace_track(struct net_device *odev,
if (odev)
netdev_tracker_free(odev, tracker);
- dev_hold(ndev);
- dev_put(odev);
+ __dev_hold(ndev);
+ __dev_put(odev);
if (ndev)
- netdev_tracker_alloc(ndev, tracker, gfp);
+ __netdev_tracker_alloc(ndev, tracker, gfp);
}
/* Carrier loss detection, dial on demand. The functions netif_carrier_on
diff --git a/net/core/dev.c b/net/core/dev.c
index f79744d99413434ad28b26dee9aeeb2893a0e3ae..1eaa0b88e3ba5d800484656f2c3420af57050294 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10172,7 +10172,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev->pcpu_refcnt = alloc_percpu(int);
if (!dev->pcpu_refcnt)
goto free_dev;
- dev_hold(dev);
+ __dev_hold(dev);
#else
refcount_set(&dev->dev_refcnt, 1);
#endif
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index b0f5344d1185be66d05cd1dc50cffc5ccfe883ef..95098d1a49bdf4cbc3ddeb4d345e4276f974a208 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -166,10 +166,10 @@ static void linkwatch_do_dev(struct net_device *dev)
netdev_state_change(dev);
}
- /* Note: our callers are responsible for
- * calling netdev_tracker_free().
+ /* Note: our callers are responsible for calling netdev_tracker_free().
+ * This is the reason we use __dev_put() instead of dev_put().
*/
- dev_put(dev);
+ __dev_put(dev);
}
static void __linkwatch_run_queue(int urgent_only)
--
2.35.0.263.gb82422642f-goog
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