Messages in this thread | | | Date | Wed, 15 Feb 2012 23:57:33 +0400 | From | Vasiliy Kulikov <> | Subject | Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree |
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On Wed, Feb 15, 2012 at 23:56 +0400, Cyrill Gorcunov wrote: > On Wed, Feb 15, 2012 at 07:43:36PM +0100, Oleg Nesterov wrote: > ... > > > > Cough... this is question I am trying to ask ;) > > > > Let me try again. To simplify, lets discuss the KCMP_VM case > > only. > > > > I do not really understand why do we need ptrace_may_access(). > > I do not see any security problems with kcmp_ptr(task->mm), but > > I am not expert. > > > > However, you added this check so I assume you have some reason. > > But this can race with execve(setuid_app) and KCMP_VM can play > > with task->mm after this task raises its caps. If this is fine, > > then why do we need ptrace_may_access? > > > > This makes me scratch the head ;) I think ptrace_may_access (or > some other security test) should remain since it's somehow weird > if non-root task will be able to find objects order from privileged > task. Thus I need to find a way how to handle execve(setuid_app). > Need to think...
Look at fs/proc/base.c:lock_trace() - it locks ->cred_guard_mutex for the whole period of time when it uses a resource.
-- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
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