Messages in this thread | | | Date | Mon, 24 Jun 2013 16:45:12 -0700 | Subject | Re: RFC: named anonymous vmas | From | John Stultz <> |
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On Mon, Jun 24, 2013 at 10:26 AM, Colin Cross <ccross@google.com> wrote: > On Mon, Jun 24, 2013 at 4:48 AM, Christoph Hellwig <hch@infradead.org> wrote: >> On Sat, Jun 22, 2013 at 12:47:29PM -0700, Alex Elsayed wrote: >>> Couldn't this be done by having a root-only tmpfs, and having a userspace >>> component that creates per-app directories with restrictive permissions on >>> startup/app install? Then each app creates files in its own directory, and >>> can pass the fds around. > > If each app gets its own writable directory that's not really > different than a world writable tmpfs. It requires something that > watches for apps to exit for any reason and cleans up their > directories, and it requires each app to come up with an unused name > when it wants to create a file, and the kernel can give you both very > cleanly.
Though, I believe having a daemon that has exclusive access to tmpfs, and creates, unlinks and passes the fd to the requesting application would provide a userspace only implementation of the second feature requirement ("without having a world-writable tmpfs that untrusted apps could fill with files"). Though I'm not sure what the proc/<pid>/maps naming would look like on the unlinked file, so it might not solve the third naming issue.
thanks -john
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