kernel.git/drivers/net/tun.c, branch linux-2.6.30.y

tun/tap: Fix crashes if open() /dev/net/tun and then poll() it. (CVE-2009-1897)

2009-07-20T03:38:47Z

commit 3c8a9c63d5fd738c261bd0ceece04d9c8357ca13 upstream. Fix NULL pointer dereference in tun_chr_pool() introduced by commit 33dccbb050bbe35b88ca8cf1228dcf3e4d4b3554 ("tun: Limit amount of queued packets per device") and triggered by this code: int fd; struct pollfd pfd; fd = open("/dev/net/tun", O_RDWR); pfd.fd = fd; pfd.events = POLLIN | POLLOUT; poll(&pfd, 1, 0); Reported-by: Eugene Kapun Signed-off-by: Mariusz Kozlowski Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tun: Fix unregister race

2009-07-02T23:49:42Z

[ Upstream commit f0a4d0e5b5bfd271e6737f7c095994835b70d450 ] It is possible for tun_chr_close to race with dellink on the a tun device. In which case if __tun_get runs before dellink but dellink runs before tun_chr_close calls unregister_netdevice we will attempt to unregister the netdevice after it is already gone. The two cases are already serialized on the rtnl_lock, so I have gone for the cheap simple fix of moving rtnl_lock to cover __tun_get in tun_chr_close. Eliminating the possibility of the tun device being unregistered between __tun_get and unregister_netdevice in tun_chr_close. Signed-off-by: Eric W. Biederman Tested-by: David Woodhouse Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tun: Fix sk_sleep races when attaching/detaching

2009-04-20T10:01:48Z

As the sk_sleep wait queue actually lives in tfile, which may be detached from the tun device, bad things will happen when we use sk_sleep after detaching. Since the tun device is the persistent data structure here (when requested by the user), it makes much more sense to have the wait queue live there. There is no reason to have it in tfile at all since the only time we can wait is if we have a tun attached. In fact we already have a wait queue in tun_struct, so we might as well use it. Reported-by: Eric W. Biederman Tested-by: Christian Borntraeger Tested-by: Patrick McHardy Signed-off-by: Herbert Xu Signed-off-by: David S. Miller

tun: Only free a netdev when all tun descriptors are closed

2009-04-20T10:01:47Z

The commit c70f182940f988448f3c12a209d18b1edc276e33 ("tun: Fix races between tun_net_close and free_netdev") fixed a race where an asynchronous deletion of a tun device can hose a poll(2) on a tun fd attached to that device. However, this came at the cost of moving the tun wait queue into the tun file data structure. The problem with this is that it imposes restrictions on when and where the tun device can access the wait queue since the tun file may change at any time due to detaching and reattaching. In particular, now that we need to use the wait queue on the receive path it becomes difficult to properly synchronise this with the detachment of the tun device. This patch solves the original race in a different way. Since the race is only because the underlying memory gets freed, we can prevent it simply by ensuring that we don't do that until all tun descriptors ever attached to the device (even if they have since be detached because they may still be sitting in poll) have been closed. This is done by using reference counting the attached tun file descriptors. The refcount in tun->sk has been reappropriated for this purpose since it was already being used for that, albeit from the opposite angle. Note that we no longer zero tfile->tun since tun_get will return NULL anyway after the refcount on tfile hits zero. Instead it represents whether this device has ever been attached to a device. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller

tun: Fix crash with non-GSO users

2009-04-14T09:09:43Z

When I made the tun driver use non-linear packets as the preferred option, it broke non-GSO users because they would end up allocating a completely non-linear packet, which triggers a crash when we call eth_type_trans. This patch reverts non-GSO users to using linear packets and adds a check to ensure that GSO users can't cause crashes in the same way. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller

tun: Fix merge error

2009-02-15T04:46:39Z

When forward-porting the tun accounting patch I managed to break the send path compltely by dropping the tun_get call. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller

Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6

2009-02-10T07:22:21Z

Conflicts: drivers/net/gianfar.c

tun: Fix unicast filter overflow

2009-02-09T01:49:17Z

Tap devices can make use of a small MAC filter set via the TUNSETTXFILTER ioctl. The filter has a set of exact matches plus a hash for imperfect filtering of additional multicast addresses. The current code is unbalanced, adding unicast addresses to the multicast hash, but only checking the hash against multicast addresses. This results in the filter dropping unicast addresses that overflow the exact filter. The fix is simply to disable the filter by leaving count set to zero if we find non-multicast addresses after the exact match table is filled. Signed-off-by: Alex Williamson Signed-off-by: David S. Miller

tun: Limit amount of queued packets per device

2009-02-06T05:25:32Z

Unlike a normal socket path, the tuntap device send path does not have any accounting. This means that the user-space sender may be able to pin down arbitrary amounts of kernel memory by continuing to send data to an end-point that is congested. Even when this isn't an issue because of limited queueing at most end points, this can also be a problem because its only response to congestion is packet loss. That is, when those local queues at the end-point fills up, the tuntap device will start wasting system time because it will continue to send data there which simply gets dropped straight away. Of course one could argue that everybody should do congestion control end-to-end, unfortunately there are people in this world still hooked on UDP, and they don't appear to be going away anywhere fast. In fact, we've always helped them by performing accounting in our UDP code, the sole purpose of which is to provide congestion feedback other than through packet loss. This patch attempts to apply the same bandaid to the tuntap device. It creates a pseudo-socket object which is used to account our packets just as a normal socket does for UDP. Of course things are a little complex because we're actually reinjecting traffic back into the stack rather than out of the stack. The stack complexities however should have been resolved by preceding patches. So this one can simply start using skb_set_owner_w. For now the accounting is essentially disabled by default for backwards compatibility. In particular, we set the cap to INT_MAX. This is so that existing applications don't get confused by the sudden arrival EAGAIN errors. In future we may wish (or be forced to) do this by default. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller

tun: Check supplemental groups in TUN/TAP driver.

2009-02-03T07:34:56Z

Michael Tokarev wrote: [] > 2, and this is the main one: How about supplementary groups? > > Here I have a valid usage case: a group of testers running various > versions of windows using KVM (kernel virtual machine), 1 at a time, > to test some software. kvm is set up to use bridge with a tap device > (there should be a way to connect to the machine). Anyone on that group > has to be able to start/stop the virtual machines. > > My first attempt - pretty obvious when I saw -g option of tunctl - is > to add group ownership for the tun device and add a supplementary group > to each user (their primary group should be different). But that fails, > since kernel only checks for egid, not any other group ids. > > What's the reasoning to not allow supplementary groups and to only check > for egid? Signed-off-by: Michael Tokarev Signed-off-by: David S. Miller