From: Cong Wang cong.wang@bytedance.com
commit 3b23a32a63219f51a5298bc55a65ecee866e79d0 upstream.
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(). We can not use seqlock here as it does not allow blocking. The writers already take RTNL anyway, so this does 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 on ioctl and rtnetlink paths.
Note, bonding also changes slave mac addresses but that requires a separate patch due to the complexity of bonding code.
Fixes: 3710becf8a58 ("net: RCU locking for simple ioctl()") Reported-by: "Gong, Sishuai" sishuai@purdue.edu Cc: Eric Dumazet eric.dumazet@gmail.com Cc: Jakub Kicinski kuba@kernel.org Signed-off-by: Cong Wang cong.wang@bytedance.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/tap.c | 7 +++---- drivers/net/tun.c | 5 ++--- include/linux/netdevice.h | 3 +++ net/core/dev.c | 42 ++++++++++++++++++++++++++++++++++++++++++ net/core/dev_ioctl.c | 20 +++++++------------- net/core/rtnetlink.c | 2 +- 6 files changed, 58 insertions(+), 21 deletions(-)
--- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -1093,10 +1093,9 @@ static long tap_ioctl(struct file *file, return -ENOLINK; } ret = 0; - u = tap->dev->type; + dev_get_mac_address(&sa, dev_net(tap->dev), tap->dev->name); if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) || - copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) || - put_user(u, &ifr->ifr_hwaddr.sa_family)) + copy_to_user(&ifr->ifr_hwaddr, &sa, sizeof(sa))) ret = -EFAULT; tap_put_tap_dev(tap); rtnl_unlock(); @@ -1111,7 +1110,7 @@ static long tap_ioctl(struct file *file, rtnl_unlock(); return -ENOLINK; } - ret = dev_set_mac_address(tap->dev, &sa, NULL); + ret = dev_set_mac_address_user(tap->dev, &sa, NULL); tap_put_tap_dev(tap); rtnl_unlock(); return ret; --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -3157,15 +3157,14 @@ static long __tun_chr_ioctl(struct file
case SIOCGIFHWADDR: /* Get hw address */ - memcpy(ifr.ifr_hwaddr.sa_data, tun->dev->dev_addr, ETH_ALEN); - ifr.ifr_hwaddr.sa_family = tun->dev->type; + dev_get_mac_address(&ifr.ifr_hwaddr, net, tun->dev->name); if (copy_to_user(argp, &ifr, ifreq_len)) ret = -EFAULT; break;
case SIOCSIFHWADDR: /* Set hw address */ - ret = dev_set_mac_address(tun->dev, &ifr.ifr_hwaddr, NULL); + ret = dev_set_mac_address_user(tun->dev, &ifr.ifr_hwaddr, NULL); break;
case TUNGETSNDBUF: --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3879,6 +3879,9 @@ int dev_pre_changeaddr_notify(struct net 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); --- a/net/core/dev.c +++ b/net/core/dev.c @@ -8686,6 +8686,48 @@ int dev_set_mac_address(struct net_devic } 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; +} +EXPORT_SYMBOL(dev_set_mac_address_user); + +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; +} +EXPORT_SYMBOL(dev_get_mac_address); + /** * dev_change_carrier - Change device carrier * @dev: device --- a/net/core/dev_ioctl.c +++ b/net/core/dev_ioctl.c @@ -123,17 +123,6 @@ static int dev_ifsioc_locked(struct net 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, s 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 */
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 case SIOCGIFFLAGS: case SIOCGIFMETRIC: case SIOCGIFMTU: - case SIOCGIFHWADDR: case SIOCGIFSLAVE: case SIOCGIFMAP: case SIOCGIFINDEX: --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -2658,7 +2658,7 @@ static int do_setlink(const struct sk_bu 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;