This is a note to let you know that I've just added the patch titled
net: add netdev->up protected by netdev_lock()
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-add-netdev-up-protected-by-netdev_lock.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 996f44c563e77c7a00e23892c4a95f664c97ffe4
Author: Jakub Kicinski <kuba@xxxxxxxxxx>
Date: Tue Jan 14 19:53:12 2025 -0800
net: add netdev->up protected by netdev_lock()
[ Upstream commit 5112457f3d8e41f987908266068af88ef9f3ab78 ]
Some uAPI (netdev netlink) hide net_device's sub-objects while
the interface is down to ensure uniform behavior across drivers.
To remove the rtnl_lock dependency from those uAPIs we need a way
to safely tell if the device is down or up.
Add an indication of whether device is open or closed, protected
by netdev->lock. The semantics are the same as IFF_UP, but taking
netdev_lock around every write to ->flags would be a lot of code
churn.
We don't want to blanket the entire open / close path by netdev_lock,
because it will prevent us from applying it to specific structures -
core helpers won't be able to take that lock from any function
called by the drivers on open/close paths.
So the state of the flag is "pessimistic", as in it may report false
negatives, but never false positives.
Reviewed-by: Joe Damato <jdamato@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Link: https://patch.msgid.link/20250115035319.559603-5-kuba@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Stable-dep-of: 011b03359038 ("Revert "net: skb: introduce and use a single page frag cache"")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 47f817bcea503..64013fd389f28 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2441,12 +2441,24 @@ struct net_device {
unsigned long gro_flush_timeout;
u32 napi_defer_hard_irqs;
+ /**
+ * @up: copy of @state's IFF_UP, but safe to read with just @lock.
+ * May report false negatives while the device is being opened
+ * or closed (@lock does not protect .ndo_open, or .ndo_close).
+ */
+ bool up;
+
/**
* @lock: netdev-scope lock, protects a small selection of fields.
* Should always be taken using netdev_lock() / netdev_unlock() helpers.
* Drivers are free to use it for other protection.
*
- * Protects: @reg_state, @net_shaper_hierarchy.
+ * Protects:
+ * @net_shaper_hierarchy, @reg_state
+ *
+ * Partially protects (writers must hold both @lock and rtnl_lock):
+ * @up
+ *
* Ordering: take after rtnl_lock.
*/
struct mutex lock;
diff --git a/net/core/dev.c b/net/core/dev.c
index 75996e1aac46c..67f2bb84db543 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1512,7 +1512,7 @@ static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
if (ret)
clear_bit(__LINK_STATE_START, &dev->state);
else {
- dev->flags |= IFF_UP;
+ netif_set_up(dev, true);
dev_set_rx_mode(dev);
dev_activate(dev);
add_device_randomness(dev->dev_addr, dev->addr_len);
@@ -1591,7 +1591,7 @@ static void __dev_close_many(struct list_head *head)
if (ops->ndo_stop)
ops->ndo_stop(dev);
- dev->flags &= ~IFF_UP;
+ netif_set_up(dev, false);
netpoll_poll_enable(dev);
}
}
diff --git a/net/core/dev.h b/net/core/dev.h
index deb5eae5749fa..e17c640c05fb9 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -111,6 +111,18 @@ void __dev_notify_flags(struct net_device *dev, unsigned int old_flags,
void unregister_netdevice_many_notify(struct list_head *head,
u32 portid, const struct nlmsghdr *nlh);
+static inline void netif_set_up(struct net_device *dev, bool value)
+{
+ if (value)
+ dev->flags |= IFF_UP;
+ else
+ dev->flags &= ~IFF_UP;
+
+ netdev_lock(dev);
+ dev->up = value;
+ netdev_unlock(dev);
+}
+
static inline void netif_set_gso_max_size(struct net_device *dev,
unsigned int size)
{
