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net: fix dev_ifsioc_locked() race condition

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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: 3710becf8a ("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>
This commit is contained in:
Cong Wang
2021-02-11 11:34:10 -08:00
committed by David S. Miller
parent 7867299cde
commit 3b23a32a63
6 changed files with 58 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
net/core/dev.c
View File

@@ -8937,6 +8937,48 @@ 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;
}
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

20
net/core/dev_ioctl.c
View File

@@ -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:

2
net/core/rtnetlink.c
View File

@@ -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;