Zhao Lei <zhaolei@xxxxxxxxxxxxxx> writes: > Hi, Mateusz Guzik > >> -----Original Message----- >> From: Mateusz Guzik [mailto:mguzik@xxxxxxxxxx] >> Sent: Thursday, February 18, 2016 4:54 AM >> To: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> >> Cc: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>; containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; >> linux-kernel@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH] Make core_pattern support namespace >> >> On Wed, Feb 17, 2016 at 02:15:24PM -0600, Eric W. Biederman wrote: >> > Mateusz Guzik <mguzik@xxxxxxxxxx> writes: >> > > On Tue, Feb 16, 2016 at 07:33:39PM +0800, Zhao Lei wrote: >> > >> For container based on namespace design, it is good to allow >> > >> each container keeping their own coredump setting. >> > > >> > > Sorry if this is a false alarm, I don't have easy means to test it, but >> > > is not this an immediate privilege escalation? >> > >> > It is. This is why we do not currently have a per namespace setting. >> > >> >> Thanks for confimation. >> >> > Solving the user mode helper problem is technically a fair amount of >> > work, if not theoretically challenging. >> > >> >> Well, I would say custom core_patterns without pipe support are still >> better than none. >> > +1. -1. The problem is solvable. It is just a matter of effort to build the necessary infrastructure and make certain everything works correctly. >> Say one would ensure a stable core_pattern (i.e. that it cannot be >> modified as it is being parsed) and a restricted set of allowed >> characters in the pattern (which would not include the pipe), validated >> when one attempts to set the pattern. >> >> Does this sound acceptable? If so, and there are no counter ideas from >> Lei, I can get around to that. >> > If we can let kernel select pipe_program in vm's filesystem, and run > pipe_program with vm's filesystem, set a pipe for core_patterm in vm > will be safe. > What is your opinion on above solution? Please see the other thread about user mode helpers that is current active on the container mailling list. > If above way is not acceptable, or impossible to realize, I also > agree your solution of limit vm setting pipe. I honestly think have a fully capable system that we have now that is capable of using setns and entering a containers context is better than something half baked. The solution either needs to support everything core_pattern does today but correctly in a container environment. To make the case that something does not need to be supported, a convincing argument needs to be presented and tested that no one ever does that. Without such an argument you will be breaking userspace in a different way. Not actually fixing things. My baseline reference implementation of all of this is that it is possible when a sufficiently privileged process writes to core_pattern to fork a child with the same environment and context as the writer. That forked child could then become a kernel thread and fork any additional children needed as user mode helpers. Eric _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
