Skip to content

Commit

Permalink
ipv4: Avoid crashing in ip_error
Browse files Browse the repository at this point in the history
ip_error does not check if in_dev is NULL before dereferencing it.

IThe following sequence of calls is possible:
CPU A                          CPU B
ip_rcv_finish
    ip_route_input_noref()
        ip_route_input_slow()
                               inetdev_destroy()
    dst_input()

With the result that a network device can be destroyed while processing
an input packet.

A crash was triggered with only unicast packets in flight, and
forwarding enabled on the only network device.   The error condition
was created by the removal of the network device.

As such it is likely the that error code was -EHOSTUNREACH, and the
action taken by ip_error (if in_dev had been accessible) would have
been to not increment any counters and to have tried and likely failed
to send an icmp error as the network device is going away.

Therefore handle this weird case by just dropping the packet if
!in_dev.  It will result in dropping the packet sooner, and will not
result in an actual change of behavior.

Fixes: 251da41 ("ipv4: Cache ip_error() routes even when not forwarding.")
Reported-by: Vittorio Gambaletta <[email protected]>
Tested-by: Vittorio Gambaletta <[email protected]>
Signed-off-by: Vittorio Gambaletta <[email protected]>
Signed-off-by: "Eric W. Biederman" <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
  • Loading branch information
ebiederm authored and davem330 committed May 22, 2015
1 parent d654976 commit 381c759
Showing 1 changed file with 4 additions and 0 deletions.
4 changes: 4 additions & 0 deletions net/ipv4/route.c
Original file line number Diff line number Diff line change
Expand Up @@ -902,6 +902,10 @@ static int ip_error(struct sk_buff *skb)
bool send;
int code;

/* IP on this device is disabled. */
if (!in_dev)
goto out;

net = dev_net(rt->dst.dev);
if (!IN_DEV_FORWARD(in_dev)) {
switch (rt->dst.error) {
Expand Down

0 comments on commit 381c759

Please sign in to comment.