From 876bfd4d0f18cd1f698249870c7e7fb944de1c26 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Thu, 6 Aug 2009 14:22:44 +0000 Subject: tun: Extend RTNL lock coverage over whole ioctl As it is, parts of the ioctl runs under the RTNL and parts of it do not. The unlocked section is still protected by the BKL, but there can be subtle races. For example, Eric Biederman and Paul Moore observed that if two threads tried to create two tun devices on the same file descriptor, then unexpected results may occur. As there isn't anything in the ioctl that is expected to sleep indefinitely, we can prevent this from occurring by extending the RTNL lock coverage. This also allows to get rid of the BKL. Finally, I changed tun_get_iff to take a tun device in order to avoid calling tun_put which would dead-lock as it also tries to take the RTNL lock. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- drivers/net/tun.c | 50 +++++++++++++++++++------------------------------- 1 file changed, 19 insertions(+), 31 deletions(-) (limited to 'drivers/net/tun.c') diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 027f7aba26af..42b6c6319bc2 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1048,20 +1048,15 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) return err; } -static int tun_get_iff(struct net *net, struct file *file, struct ifreq *ifr) +static int tun_get_iff(struct net *net, struct tun_struct *tun, + struct ifreq *ifr) { - struct tun_struct *tun = tun_get(file); - - if (!tun) - return -EBADFD; - DBG(KERN_INFO "%s: tun_get_iff\n", tun->dev->name); strcpy(ifr->ifr_name, tun->dev->name); ifr->ifr_flags = tun_flags(tun); - tun_put(tun); return 0; } @@ -1105,8 +1100,8 @@ static int set_offload(struct net_device *dev, unsigned long arg) return 0; } -static int tun_chr_ioctl(struct inode *inode, struct file *file, - unsigned int cmd, unsigned long arg) +static long tun_chr_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) { struct tun_file *tfile = file->private_data; struct tun_struct *tun; @@ -1128,34 +1123,32 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, (unsigned int __user*)argp); } + rtnl_lock(); + tun = __tun_get(tfile); if (cmd == TUNSETIFF && !tun) { - int err; - ifr.ifr_name[IFNAMSIZ-1] = '\0'; - rtnl_lock(); - err = tun_set_iff(tfile->net, file, &ifr); - rtnl_unlock(); + ret = tun_set_iff(tfile->net, file, &ifr); - if (err) - return err; + if (ret) + goto unlock; if (copy_to_user(argp, &ifr, sizeof(ifr))) - return -EFAULT; - return 0; + ret = -EFAULT; + goto unlock; } - + ret = -EBADFD; if (!tun) - return -EBADFD; + goto unlock; DBG(KERN_INFO "%s: tun_chr_ioctl cmd %d\n", tun->dev->name, cmd); ret = 0; switch (cmd) { case TUNGETIFF: - ret = tun_get_iff(current->nsproxy->net_ns, file, &ifr); + ret = tun_get_iff(current->nsproxy->net_ns, tun, &ifr); if (ret) break; @@ -1201,7 +1194,6 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, case TUNSETLINK: /* Only allow setting the type when the interface is down */ - rtnl_lock(); if (tun->dev->flags & IFF_UP) { DBG(KERN_INFO "%s: Linktype set failed because interface is up\n", tun->dev->name); @@ -1211,7 +1203,6 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, DBG(KERN_INFO "%s: linktype set to %d\n", tun->dev->name, tun->dev->type); ret = 0; } - rtnl_unlock(); break; #ifdef TUN_DEBUG @@ -1220,9 +1211,7 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, break; #endif case TUNSETOFFLOAD: - rtnl_lock(); ret = set_offload(tun->dev, arg); - rtnl_unlock(); break; case TUNSETTXFILTER: @@ -1230,9 +1219,7 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, ret = -EINVAL; if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV) break; - rtnl_lock(); ret = update_filter(&tun->txflt, (void __user *)arg); - rtnl_unlock(); break; case SIOCGIFHWADDR: @@ -1248,9 +1235,7 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, DBG(KERN_DEBUG "%s: set hw address: %pM\n", tun->dev->name, ifr.ifr_hwaddr.sa_data); - rtnl_lock(); ret = dev_set_mac_address(tun->dev, &ifr.ifr_hwaddr); - rtnl_unlock(); break; case TUNGETSNDBUF: @@ -1273,7 +1258,10 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file, break; }; - tun_put(tun); +unlock: + rtnl_unlock(); + if (tun) + tun_put(tun); return ret; } @@ -1361,7 +1349,7 @@ static const struct file_operations tun_fops = { .write = do_sync_write, .aio_write = tun_chr_aio_write, .poll = tun_chr_poll, - .ioctl = tun_chr_ioctl, + .unlocked_ioctl = tun_chr_ioctl, .open = tun_chr_open, .release = tun_chr_close, .fasync = tun_chr_fasync -- cgit v1.2.3