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authorCong Wang <cong.wang@bytedance.com>2021-02-11 22:34:10 +0300
committerDavid S. Miller <davem@davemloft.net>2021-02-12 05:14:19 +0300
commit3b23a32a63219f51a5298bc55a65ecee866e79d0 (patch)
tree79f9a923b4679addfc28e39340e9834b922f7e40 /drivers/net/tun.c
parent7867299cde34e9c2d2c676f2a384a9d5853b914d (diff)
downloadlinux-3b23a32a63219f51a5298bc55a65ecee866e79d0.tar.xz
net: fix dev_ifsioc_locked() race condition
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>
Diffstat (limited to 'drivers/net/tun.c')
-rw-r--r--drivers/net/tun.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 62690baa19bc..fc86da7f1628 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3107,15 +3107,14 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
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: