Messages in this thread | | | Date | Fri, 25 Apr 2014 23:52:20 +0300 | Subject | Re: Kernel panic at Ubuntu: IMA + Apparmor | From | Dmitry Kasatkin <> |
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On 25 April 2014 23:45, Eric W. Biederman <ebiederm@xmission.com> wrote: > Dmitry Kasatkin <dmitry.kasatkin@gmail.com> writes: > >> On 25 April 2014 23:01, Oleg Nesterov <oleg@redhat.com> wrote: >>> On 04/25, Eric W. Biederman wrote: >>>> >>>> Oleg Nesterov <oleg@redhat.com> writes: >>>> >>>> > Well. I _think_ that __fput() and ima_file_free() in particular should not >>>> > depend on current and/or current->nsproxy. If nothing else, fput() can be >>>> > called by the unrelated task which looks into /proc/pid/. >>>> > >>>> > But again, task_work_add() has more and more users, and it seems that even >>>> > __fput() paths can do "everything", so perhaps it would be safer to allow >>>> > to use ->nsproxy in task_work_run. >>>> >>>> Like I said, give me a clear motivating case. >>> >>> I agree, we need a reason. Currently I do not see one. >>> >>>> Right now not allowing >>>> nsproxy is turning up bugs in __fput. Which seems like a good thing. >>> >>> This is what I certainly agree with ;) >>> >> >> Hi, >> >> IMA uses kernel_read API which does not know anything about caller. >> And of course security frameworks are at guard as usual. >> >> Exactly after reading first Eric's respons, I thought why to scratch >> the head when task work queues are indeed designed for tasks... > > __fput has no guarantee of running in the task that close the file > descriptor. If your code depends on that your code is broken. > >> And if you to dig for the history, IMA-appraisal was stuck due to >> lockdep reporting even though it was on non-everlaping cases. >> IIRC files vs. directories... >> >> After that IIRC Al Viro discussed about delayed fput and IIRC Oleg >> (sorry if I am wrong) introduced task work queues. >> >> So IMA-appraisal was able to be upstreamed... That was ~3.4 time frame, IIRC >> >> Name space also dated around ~3.4?? >> Apparmor namespace change was also around that time. >> >> 3.10 introduces this name space order change and broke IMA-appraisal. > > IMA-appraisal is fundamentally broken because I can take a mandatory > file lock and prevent IMA-apprasial. >
What file lock are you talking about? IMA-appraisal does not depends on file locks...
> Using kernel_read is what allows this. > >> Isn't it a clear motivating case??? > > kernel_read is not appropriate for IMA use. The rest of this is just > the messenger. > > IMA needs to use a cousin of kernel_read that operates at a lower level > than vfs_read. A function that all of the permission checks and the > fsnotify work. > > I am sorry to be the bearer of bad news. But kernel_read is totally > inappropriate for IMA. >
So you break IMA-appraisal and declare that it cannot be used now?
> Eric >
-- Thanks, Dmitry
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