Messages in this thread | | | Date | Thu, 28 Apr 2005 15:08:19 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH] private mounts |
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Hi!
> > > Is it possible to limit all these from kernelspace? Probably yes, > > > although a timeout for operations is something that cuts either way. > > > And the compexity of these checks would probably be orders of > > > magnitude higher then the check we are currently discussing. > > > > Yes ... but does the check we are discussing really solve the > > problem? > > > > Let's say that you attempt to export home directories of users by a > > user-space NFS daemon. This daemon probably changes its fsuid to > > match the remote user, so the check happily accepts the access and > > the user is able to lock up the daemon. > > Valid point. The only defense is that when a program set's fsuid, > it's performing the operation "on behalf of the user". So the user is > actually doing DoS against himself. > > Of course this is not strictly true. E.g. in the userspace NFS case > it's probably a DoS against all users of the mount.
Exactly. So can we simply merge root-only fuse, and then worry how to make it safe with user-mounted fuse. See your own unfsd example why user-mounting is bad.
One possible solution would be to have root-owned fused that talks to user-owned fused-s and checks they are behaving correctly?
Second is somehow improving those two lines this long thread is all about...
Pavel -- 64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms
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