From: Cong Wang <cong.w...@bytedance.com>
dev_ifsioc_locked() is called with only RCU read lock, so when
there is a parallel writer changing the mac address, it could
get a partially updated mac address, as shown below:
Thread 1 Thread 2
// eth_commit_mac_addr_change()
memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
// dev_ifsioc_locked()
memcpy(ifr->ifr_hwaddr.sa_data,
dev->dev_addr,...);
Close this race condition by guarding them with a RW semaphore,
like netdev_get_name(). The writers take RTNL anyway, so this
will not affect the slow path. To avoid bothering existing
dev_set_mac_address() callers in drivers, introduce a new wrapper
just for user-facing callers in ioctl and rtnetlink.
Fixes: 3710becf8a58 ("net: RCU locking for simple ioctl()")
Reported-by: "Gong, Sishuai" <sish...@purdue.edu>
Cc: Eric Dumazet <eric.duma...@gmail.com>
Cc: Jakub Kicinski <k...@kernel.org>
Signed-off-by: Cong Wang <cong.w...@bytedance.com>
---
include/linux/netdevice.h | 3 +++
net/core/dev.c | 40 +++++++++++++++++++++++++++++++++++++++
net/core/dev_ioctl.c | 20 +++++++-------------
net/core/rtnetlink.c | 2 +-
4 files changed, 51 insertions(+), 14 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e9e7ada07ea1..8f13d3177130 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3907,6 +3907,9 @@ int dev_pre_changeaddr_notify(struct net_device *dev,
const char *addr,
struct netlink_ext_ack *extack);
int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
struct netlink_ext_ack *extack);
+int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
+ struct netlink_ext_ack *extack);
+int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name);
int dev_change_carrier(struct net_device *, bool new_carrier);
int dev_get_phys_port_id(struct net_device *dev,
struct netdev_phys_item_id *ppid);
diff --git a/net/core/dev.c b/net/core/dev.c
index aae116d059da..ecc7914784d2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8773,6 +8773,46 @@ int dev_set_mac_address(struct net_device *dev, struct
sockaddr *sa,
}
EXPORT_SYMBOL(dev_set_mac_address);
+static DECLARE_RWSEM(dev_addr_sem);
+
+int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
+ struct netlink_ext_ack *extack)
+{
+ int ret;
+
+ down_write(&dev_addr_sem);
+ ret = dev_set_mac_address(dev, sa, extack);
+ up_write(&dev_addr_sem);
+ return ret;
+}
+
+int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name)
+{
+ size_t size = sizeof(sa->sa_data);
+ struct net_device *dev;
+ int ret = 0;
+
+ down_read(&dev_addr_sem);
+ rcu_read_lock();
+
+ dev = dev_get_by_name_rcu(net, dev_name);
+ if (!dev) {
+ ret = -ENODEV;
+ goto unlock;
+ }
+ if (!dev->addr_len)
+ memset(sa->sa_data, 0, size);
+ else
+ memcpy(sa->sa_data, dev->dev_addr,
+ min_t(size_t, size, dev->addr_len));
+ sa->sa_family = dev->type;
+
+unlock:
+ rcu_read_unlock();
+ up_read(&dev_addr_sem);
+ return ret;
+}
+
/**
* dev_change_carrier - Change device carrier
* @dev: device
diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index db8a0ff86f36..478d032f34ac 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -123,17 +123,6 @@ static int dev_ifsioc_locked(struct net *net, struct ifreq
*ifr, unsigned int cm
ifr->ifr_mtu = dev->mtu;
return 0;
- case SIOCGIFHWADDR:
- if (!dev->addr_len)
- memset(ifr->ifr_hwaddr.sa_data, 0,
- sizeof(ifr->ifr_hwaddr.sa_data));
- else
- memcpy(ifr->ifr_hwaddr.sa_data, dev->dev_addr,
- min(sizeof(ifr->ifr_hwaddr.sa_data),
- (size_t)dev->addr_len));
- ifr->ifr_hwaddr.sa_family = dev->type;
- return 0;
-
case SIOCGIFSLAVE:
err = -EINVAL;
break;
@@ -274,7 +263,7 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr,
unsigned int cmd)
case SIOCSIFHWADDR:
if (dev->addr_len > sizeof(struct sockaddr))
return -EINVAL;
- return dev_set_mac_address(dev, &ifr->ifr_hwaddr, NULL);
+ return dev_set_mac_address_user(dev, &ifr->ifr_hwaddr, NULL);
case SIOCSIFHWBROADCAST:
if (ifr->ifr_hwaddr.sa_family != dev->type)
@@ -418,6 +407,12 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct
ifreq *ifr, bool *need_c
*/
switch (cmd) {
+ case SIOCGIFHWADDR:
+ dev_load(net, ifr->ifr_name);
+ ret = dev_get_mac_address(&ifr->ifr_hwaddr, net, ifr->ifr_name);
+ if (colon)
+ *colon = ':';
+ return ret;
/*
* These ioctl calls:
* - can be done by all.
@@ -427,7 +422,6 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct
ifreq *ifr, bool *need_c
case SIOCGIFFLAGS:
case SIOCGIFMETRIC:
case SIOCGIFMTU:
- case SIOCGIFHWADDR:
case SIOCGIFSLAVE:
case SIOCGIFMAP:
case SIOCGIFINDEX:
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index c313aaf2bce1..0edc0b2baaa4 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2660,7 +2660,7 @@ static int do_setlink(const struct sk_buff *skb,
sa->sa_family = dev->type;
memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
dev->addr_len);
- err = dev_set_mac_address(dev, sa, extack);
+ err = dev_set_mac_address_user(dev, sa, extack);
kfree(sa);
if (err)
goto errout;
--
2.25.1
