Commit 1bb86cf8 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

net: protect threaded status of NAPI with netdev_lock() 



Now that NAPI instances can't come and go without holding
netdev->lock we can trivially switch from rtnl_lock() to
netdev_lock() for setting netdev->threaded via sysfs.

Note that since we do not lock netdev_lock around sysfs
calls in the core we don't have to "trylock" like we do
with rtnl_lock.

Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115035319.559603-9-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent eeeec1d4

include/linux/netdevice.h

+11 −2
Original line number Diff line number Diff line
@@ -384,7 +384,7 @@ struct napi_struct { 
	int			rx_count; /* length of rx_list */

	unsigned int		napi_id; /* protected by netdev_lock */

	struct hrtimer		timer;

	struct task_struct	*thread;

	struct task_struct	*thread; /* protected by netdev_lock */

	unsigned long		gro_flush_timeout;

	unsigned long		irq_suspend_timeout;

	u32			defer_hard_irqs;
@@ -2451,11 +2451,13 @@ struct net_device { 
	 * Drivers are free to use it for other protection.

	 *

	 * Protects:

	 *	@napi_list, @net_shaper_hierarchy, @reg_state

	 *	@napi_list, @net_shaper_hierarchy, @reg_state, @threaded

	 *

	 * Partially protects (writers must hold both @lock and rtnl_lock):

	 *	@up

	 *

	 * Also protects some fields in struct napi_struct.

	 *

	 * Ordering: take after rtnl_lock.

	 */

	struct mutex		lock;
@@ -2697,6 +2699,13 @@ static inline void netdev_assert_locked(struct net_device *dev) 
	lockdep_assert_held(&dev->lock);

}



static inline void netdev_assert_locked_or_invisible(struct net_device *dev)

{

	if (dev->reg_state == NETREG_REGISTERED ||

	    dev->reg_state == NETREG_UNREGISTERING)

		netdev_assert_locked(dev);

}



static inline void netif_napi_set_irq(struct napi_struct *napi, int irq)

{

	napi->irq = irq;

net/core/dev.c

+2 −0
Original line number Diff line number Diff line
@@ -6785,6 +6785,8 @@ int dev_set_threaded(struct net_device *dev, bool threaded) 
	struct napi_struct *napi;

	int err = 0;



	netdev_assert_locked_or_invisible(dev);



	if (dev->threaded == threaded)

		return 0;

net/core/net-sysfs.c

+32 −2
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ static const char fmt_uint[] = "%u\n"; 
static const char fmt_ulong[] = "%lu\n";

static const char fmt_u64[] = "%llu\n";



/* Caller holds RTNL or RCU */

/* Caller holds RTNL, netdev->lock or RCU */

static inline int dev_isalive(const struct net_device *dev)

{

	return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
@@ -108,6 +108,36 @@ static ssize_t netdev_store(struct device *dev, struct device_attribute *attr, 
	return ret;

}



/* Same as netdev_store() but takes netdev_lock() instead of rtnl_lock() */

static ssize_t

netdev_lock_store(struct device *dev, struct device_attribute *attr,

		  const char *buf, size_t len,

		  int (*set)(struct net_device *, unsigned long))

{

	struct net_device *netdev = to_net_dev(dev);

	struct net *net = dev_net(netdev);

	unsigned long new;

	int ret;



	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))

		return -EPERM;



	ret = kstrtoul(buf, 0, &new);

	if (ret)

		return ret;



	netdev_lock(netdev);



	if (dev_isalive(netdev)) {

		ret = (*set)(netdev, new);

		if (ret == 0)

			ret = len;

	}

	netdev_unlock(netdev);



	return ret;

}



NETDEVICE_SHOW_RO(dev_id, fmt_hex);

NETDEVICE_SHOW_RO(dev_port, fmt_dec);

NETDEVICE_SHOW_RO(addr_assign_type, fmt_dec);
@@ -638,7 +668,7 @@ static ssize_t threaded_store(struct device *dev, 
			      struct device_attribute *attr,

			      const char *buf, size_t len)

{

	return netdev_store(dev, attr, buf, len, modify_napi_threaded);

	return netdev_lock_store(dev, attr, buf, len, modify_napi_threaded);

}

static DEVICE_ATTR_RW(threaded);