From: Andrea Arcangeli <aarcange@redhat.com> To: Mike Rapoport <rppt@linux.ibm.com> Cc: Peter Xu <peterx@redhat.com>, linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>, Hugh Dickins <hughd@google.com>, Luis Chamberlain <mcgrof@kernel.org>, Maxime Coquelin <maxime.coquelin@redhat.com>, Maya Gokhale <gokhale2@llnl.gov>, Jerome Glisse <jglisse@redhat.com>, Pavel Emelyanov <xemul@virtuozzo.com>, Johannes Weiner <hannes@cmpxchg.org>, Martin Cracauer <cracauer@cons.org>, Denis Plotnikov <dplotnikov@virtuozzo.com>, linux-mm@kvack.org, Marty McFadden <mcfadden8@llnl.gov>, Mike Kravetz <mike.kravetz@oracle.com>, Mike Rapoport <rppt@linux.vnet.ibm.com>, Kees Cook <keescook@chromium.org>, Mel Gorman <mgorman@suse.de>, "Kirill A . Shutemov" <kirill@shutemov.name>, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Dr . David Alan Gilbert" <dgilbert@redhat.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd Date: Tue, 19 Mar 2019 14:07:29 -0400 [thread overview] Message-ID: <20190319180729.GA27618@redhat.com> (raw) In-Reply-To: <20190319071104.GA6392@rapoport-lnx> Hello, On Tue, Mar 19, 2019 at 09:11:04AM +0200, Mike Rapoport wrote: > Hi Peter, > > On Tue, Mar 19, 2019 at 11:07:22AM +0800, Peter Xu wrote: > > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control > > whether userfaultfd is allowed by unprivileged users. When this is > > set to zero, only privileged users (root user, or users with the > > CAP_SYS_PTRACE capability) will be able to use the userfaultfd > > syscalls. > > > > Suggested-by: Andrea Arcangeli <aarcange@redhat.com> > > Suggested-by: Mike Rapoport <rppt@linux.vnet.ibm.com> > > Signed-off-by: Peter Xu <peterx@redhat.com> > > Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> > > Just one minor note below This looks fine with me too. > > + if (!sysctl_unprivileged_userfaultfd && !capable(CAP_SYS_PTRACE)) > > + return -EPERM; The only difference between the bpf sysctl and the userfaultfd sysctl this way is that the bpf sysctl adds the CAP_SYS_ADMIN capability requirement, while userfaultfd adds the CAP_SYS_PTRACE requirement, because the userfaultfd monitor is more likely to need CAP_SYS_PTRACE already if it's doing other kind of tracking on processes runtime, in addition of userfaultfd. In other words both syscalls works only for root, when the two sysctl are opt-in set to 1. Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com> To: Mike Rapoport <rppt@linux.ibm.com> Cc: Peter Xu <peterx@redhat.com>, linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>, Hugh Dickins <hughd@google.com>, Luis Chamberlain <mcgrof@kernel.org>, Maxime Coquelin <maxime.coquelin@redhat.com>, Maya Gokhale <gokhale2@llnl.gov>, Jerome Glisse <jglisse@redhat.com>, Pavel Emelyanov <xemul@virtuozzo.com>, Johannes Weiner <hannes@cmpxchg.org>, Martin Cracauer <cracauer@cons.org>, Denis Plotnikov <dplotnikov@virtuozzo.com>, linux-mm@kvack.org, Marty McFadden <mcfadden8@llnl.gov>, Mike Kravetz <mike.kravetz@oracle.com>, Mike Rapoport <rppt@linux.vnet.ibm.com>, Kees Cook <keescook@chromium.org>, Mel Gorman <mgorman@suse.de>, "Kirill A . Shutemov" <kirill@shutemov.name>, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, Dr Subject: Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd Date: Tue, 19 Mar 2019 14:07:29 -0400 [thread overview] Message-ID: <20190319180729.GA27618@redhat.com> (raw) In-Reply-To: <20190319071104.GA6392@rapoport-lnx> Hello, On Tue, Mar 19, 2019 at 09:11:04AM +0200, Mike Rapoport wrote: > Hi Peter, > > On Tue, Mar 19, 2019 at 11:07:22AM +0800, Peter Xu wrote: > > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control > > whether userfaultfd is allowed by unprivileged users. When this is > > set to zero, only privileged users (root user, or users with the > > CAP_SYS_PTRACE capability) will be able to use the userfaultfd > > syscalls. > > > > Suggested-by: Andrea Arcangeli <aarcange@redhat.com> > > Suggested-by: Mike Rapoport <rppt@linux.vnet.ibm.com> > > Signed-off-by: Peter Xu <peterx@redhat.com> > > Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> > > Just one minor note below This looks fine with me too. > > + if (!sysctl_unprivileged_userfaultfd && !capable(CAP_SYS_PTRACE)) > > + return -EPERM; The only difference between the bpf sysctl and the userfaultfd sysctl this way is that the bpf sysctl adds the CAP_SYS_ADMIN capability requirement, while userfaultfd adds the CAP_SYS_PTRACE requirement, because the userfaultfd monitor is more likely to need CAP_SYS_PTRACE already if it's doing other kind of tracking on processes runtime, in addition of userfaultfd. In other words both syscalls works only for root, when the two sysctl are opt-in set to 1. Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
next prev parent reply other threads:[~2019-03-20 6:09 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-19 3:07 [PATCH v2 0/1] userfaultfd: allow to forbid unprivileged users Peter Xu 2019-03-19 3:07 ` Peter Xu 2019-03-19 3:07 ` [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd Peter Xu 2019-03-19 3:07 ` Peter Xu 2019-03-19 7:11 ` Mike Rapoport 2019-03-19 7:11 ` Mike Rapoport 2019-03-19 18:07 ` Andrea Arcangeli [this message] 2019-03-19 18:07 ` Andrea Arcangeli 2019-03-19 18:02 ` Andrew Morton 2019-03-19 18:02 ` Andrew Morton 2019-03-19 18:28 ` Dr. David Alan Gilbert 2019-03-19 18:28 ` Dr. David Alan Gilbert 2019-03-20 0:20 ` Peter Xu 2019-03-20 0:20 ` Peter Xu 2019-03-20 19:01 ` Andrea Arcangeli 2019-03-20 19:01 ` Andrea Arcangeli 2019-03-21 13:43 ` Luis Chamberlain 2019-03-21 13:43 ` Luis Chamberlain 2019-03-21 21:06 ` Andrea Arcangeli 2019-03-21 21:06 ` Andrea Arcangeli 2019-04-23 22:19 ` Kees Cook 2019-04-23 22:19 ` Kees Cook 2019-04-23 22:19 ` Kees Cook 2020-05-27 6:54 Xiaoming Ni 2020-05-27 14:21 ` Peter Xu 2020-05-28 8:50 ` Xiaoming Ni 2020-05-28 12:49 ` Peter Xu
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