diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2009-01-20 10:57:48 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-01-21 16:00:43 -0800 |
| commit | a7385ba21102a90f902055f9f185ca02bf62fa43 (patch) | |
| tree | 93aa0f83a70f704e33ed378b2ad4636533bd7bde | |
| parent | 74a3e5a71c9b54c63bff978e9cafbcef67600f0b (diff) | |
tun: Fix races in tun_set_iff
It is possible for two different tasks with access to the same file
descriptor to call tun_set_iff on it at the same time and race to
attach to a tap device. Prevent this by placing all of the logic to
attach to a file descriptor in one function and testing the file
descriptor to be certain it is not already attached to another tun
device.
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | drivers/net/tun.c | 48 |
1 files changed, 32 insertions, 16 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 17923a50853..20ef14dc560 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -106,6 +106,31 @@ struct tun_struct { #endif }; +static int tun_attach(struct tun_struct *tun, struct file *file) +{ + const struct cred *cred = current_cred(); + + ASSERT_RTNL(); + + if (file->private_data) + return -EINVAL; + + if (tun->attached) + return -EBUSY; + + /* Check permissions */ + if (((tun->owner != -1 && cred->euid != tun->owner) || + (tun->group != -1 && cred->egid != tun->group)) && + !capable(CAP_NET_ADMIN)) + return -EPERM; + + file->private_data = tun; + tun->attached = 1; + get_net(dev_net(tun->dev)); + + return 0; +} + /* TAP filterting */ static void addr_hash_set(u32 *mask, const u8 *addr) { @@ -695,7 +720,6 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) { struct tun_struct *tun; struct net_device *dev; - const struct cred *cred = current_cred(); int err; dev = __dev_get_by_name(net, ifr->ifr_name); @@ -707,17 +731,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) else return -EINVAL; - if (tun->attached) - return -EBUSY; - - /* Check permissions */ - if (((tun->owner != -1 && - cred->euid != tun->owner) || - (tun->group != -1 && - cred->egid != tun->group)) && - !capable(CAP_NET_ADMIN)) { - return -EPERM; - } + err = tun_attach(tun, file); + if (err < 0) + return err; } else { char *name; @@ -766,6 +782,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) err = register_netdevice(tun->dev); if (err < 0) goto err_free_dev; + + err = tun_attach(tun, file); + if (err < 0) + goto err_free_dev; } DBG(KERN_INFO "%s: tun_set_iff\n", tun->dev->name); @@ -785,10 +805,6 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) else tun->flags &= ~TUN_VNET_HDR; - file->private_data = tun; - tun->attached = 1; - get_net(dev_net(tun->dev)); - /* Make sure persistent devices do not get stuck in * xoff state. */ |