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tun: Fix minor race in TUNSETLINK ioctl handling.

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Noticed by Alan Cox.

The IFF_UP test is a bit racey, because other entities
outside of this driver's ioctl handler can modify that
state, even though this ioctl handler runs under
lock_kernel().

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2008-04-23 19:37:58 -07:00
parent 8c0469cdd0
commit 48abfe05cd
1 changed files with 9 additions and 2 deletions
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11
drivers/net/tun.c
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@ -668,16 +668,23 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file,
break;
case TUNSETLINK:
{
int ret;
/* 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);
return -EBUSY;
ret = -EBUSY;
} else {
tun->dev->type = (int) arg;
DBG(KERN_INFO "%s: linktype set to %d\n", tun->dev->name, tun->dev->type);
ret = 0;
}
break;
rtnl_unlock();
return ret;
}
#ifdef TUN_DEBUG
case TUNSETDEBUG: