bridge: Only call /sbin/bridge-stp for the initial network namespace

[ Upstream commit ff62198553e43cdffa9d539f6165d3e83f8a42bc ]

[I stole this patch from Eric Biederman. He wrote:]

> There is no defined mechanism to pass network namespace information
> into /sbin/bridge-stp therefore don't even try to invoke it except
> for bridge devices in the initial network namespace.
>
> It is possible for unprivileged users to cause /sbin/bridge-stp to be
> invoked for any network device name which if /sbin/bridge-stp does not
> guard against unreasonable arguments or being invoked twice on the
> same network device could cause problems.

[Hannes: changed patch using netns_eq]

Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 886f6d6dc48a3f8c2749dc9c04dc422e248c5f35..3995a66c3e4ea517635228ffc8c9493bfdd6d9d4 100644 (file)
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -128,7 +128,10 @@ static void br_stp_start(struct net_bridge *br)
        char *argv[] = { BR_STP_PROG, br->dev->name, "start", NULL };
        char *envp[] = { NULL };
 
-       r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
+       if (net_eq(dev_net(br->dev), &init_net))
+               r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
+       else
+               r = -ENOENT;
 
        spin_lock_bh(&br->lock);