On Mon, Aug 16, 2010 at 11:39:47PM -0400, Eric Paris wrote: > On Mon, 2010-08-16 at 22:32 +0200, Andreas Gruenbacher wrote: > > On Saturday 07 August 2010 21:15:14 Eric Paris wrote: > > > On Fri, 2010-08-06 at 20:06 -0400, Christoph Hellwig wrote: > > > > I'm also totally missing on any re-post of these patches or discussion > > > > of the changes during the last development window. > > > > > > I just searched lkml an fsdevel where I usually send everything don't > > > see then. I totally failed. > > > > Oh yes. > > > > This introduces two new syscalls which will be impossible to fix up after the > > fact, and those system calls are poorly documented: commits 2a3edf86 and > > 52c923dd document the initial versions (in the commit message!), but > > subsequent commits then extend that interface. The interface for replying to > > events is not documented at all beyond the example code [1]. There is no > > documentation in Documentation/filesystems/, either. > > > > [1] http://people.redhat.com/~eparis/fanotify/ > > I'll work on documentation. Although it should be pointed out that the > interface was sent to list many times with lots of discussion and > feedback. The only patches that didn't make the list were the last > couple which changed internal notification semantics (and fscked with > fput() but that patch, which caused problems, was specifically pointed > out in this thread and reverted). > > > Q: What happens when a process watching for FAN_OPEN_PERM or FAN_ACCESS_PERM > > events exits or dies while events are in flight? I can't see anything in the > > code that would wake sleeping processes up when the fsnotify_group of the > > listener is torn down. > > We can get stuck. There was code which cleaned that up, but it got > accidentally removed long ago when, upon review on list, I was told to > remove all timeout code. It's easy enough to fix up. I'll post a patch > this week. > > > Q: What prevents the system from going out of memory when a listener decides > > to stop reading events or simply can't keep up? There doesn't seem to be a > > limit on the queue depth. Listeners currently need CAP_SYS_ADMIN, but somehow > > limiting the queue depth and throttling when things start to go bad still > > sounds like a reasonable thing to do, right?) > > It's an interesting question and obviously one that I've thought about. > You remember when we talked previously I said the hardest part left was > allowing non-root users to use the interface. It gets especially > difficult when thinking about perm-events. I was specifically told not > to timeout or drop those. But when dealing with non-root users using > perm events? As for pure notification we can do something like inotify > does quite easily. > > I'm not certain exactly what the best semantics are for non trusted > users, so I didn't push any patches that way. Suggestions welcome :) Hi Eric, Sorry I haven't had a chance to look at the perm events. I think user namespace and containers folks might be interested in them for non-root users though. [Adding userns/containers folks to Cc] I'm guessing non-trusted users can be restricted to only get perm events on stuff they already own. Plus make perm events by non-trusted users unreliable yet failsafe -- return EACESS/EPERM when we have to timeout or drop the events if I understand the issues correctly. Those rules plus user namespaces would still be quite useful I think. Do they seem reasonable to implement? Am I forgetting anything important? Cheers, -Matt Helsley _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
