Messages in this thread | | | From | Richard Weinberger <> | Subject | user controllable usermodehelper in br_stp_if.c | Date | Sun, 29 Nov 2015 23:43:09 +0100 |
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Hi!
By spawning new network and user namesapces an unprivileged user is able to execute /sbin/bridge-stp within the initial mount namespace with global root rights. While this cannot directly be used to break out of a container or gain global root rights it could be used by exploit writers as valuable building block.
e.g. $ unshare -U -r -n /bin/sh $ brctl addbr br0 $ brctl stp br0 on # this will execute /sbin/bridge-stp
As this mechanism clearly cannot work with containers and seems to be legacy code I suggest not calling call_usermodehelper() at all if we're not in the initial user namespace. What do you think?
Thanks, //richard
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