Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 12 Jan 2012 17:17:31 -0800 | Subject | Re: [PATCH PLACEHOLDER 1/3] fs/exec: "always_unprivileged" patch |
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On Thu, Jan 12, 2012 at 5:11 PM, Andrew Lutomirski <luto@mit.edu> wrote: > > What if you're a daemon that needs something like CAP_NET_BIND but > also wants to be able to run other helpers without CAP_NET_BIND? > > (Also, preventing dropping of privileges will probably make a patch > more complicted -- I'll have to find and update all the places that > allow dropping privileges.)
Hey, if it actually makes it more complicated to say "don't change privileges", then I guess my argument that it should be simpler is wrong.
That said, the thing you bring up is *not* the actual use-case for the suggestion. The use-case is a "run untrusted code". So the use-case would be to set the flag after you've dropped CAP_NET_BIND, and *before* you actually run the other helpers. You clearly must have a fork() or something like that there, since you want to keep the NET_BIND in the original daemon.
So I don't t think your example is actually the expected situation. The obvious approach for your example is - run deamon with CAP_NET_BIND - per connection, fork, drop privileges in child, then set "restricted" flag, and run the untrusted code.
(where the restricted mode setting may well obviously also do other things - like limit allowed system calls etc)
Linus
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