From: Jason Gunthorpe <jgg@ziepe.ca>
To: Kees Cook <keescook@chromium.org>
Cc: "Ruhl, Michael J" <michael.j.ruhl@intel.com>,
Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
Leon Romanovsky <leonro@mellanox.com>,
RDMA mailing list <linux-rdma@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Feras Daoud <ferasda@mellanox.com>,
Haggai Eran <haggaie@mellanox.com>,
Saeed Mahameed <saeedm@mellanox.com>,
linux-netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH rdma-next 3/6] RDMA/ucontext: Do not allow BAR mappings to be executable
Date: Mon, 22 Apr 2019 09:51:38 -0300 [thread overview]
Message-ID: <20190422125138.GB21588@ziepe.ca> (raw)
In-Reply-To: <CAGXu5jKE-o11YeYyLOL4arJA-O5_BKYdtrdfLthFsm2pfjGnGg@mail.gmail.com>
On Thu, Apr 18, 2019 at 02:23:26AM -0500, Kees Cook wrote:
> On Thu, Apr 18, 2019 at 2:01 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Thu, Apr 18, 2019 at 01:30:07AM -0500, Kees Cook wrote:
> >
> > > Anything running with READ_IMPLIES_EXEC (i.e. a gnu stack marked WITH
> > > execute) should be considered broken. Now, the trouble is that this
> > > personality flag is carried across execve(), so if you have a launcher
> > > that doesn't fix up the personality for children, you'll see this
> > > spread all over your process tree. What is doing rdma mmap calls with
> > > an executable stack? That really feels to me like the real source of
> > > the problem.
> >
> > Apparently the Fortran runtime forces the READ_IMPLIES_EXEC and
> > requires it for some real reason or another - Fortran and RDMA go
> > together in alot of cases.
>
> That's pretty unfortunate for the security of the resulting proceses. :(
I think it probably arises from a need for exec stacks in the
runtime... That Linux escalates that to full READ_IMPLIES_EXEC seems
quite unfortunate. Hopefully your patch will get accepted as it makes
a lot of sense.
> I wonder if we could simply make devtmpfs ignore READ_IMPLIES_EXEC
> entirely, though? And I wonder if we could defang READ_IMPLIES_EXEC a
> bit in general. It was _supposed_ to be for the cases where binaries
> were missing exec bits and a processor was just gaining NX ability. I
> know this has been discussed before... ah-ha, here it is:
> http://lkml.kernel.org/r/1462963502-11636-1-git-send-email-hecmargi@upv.es
Globally banning VM_EXEC from char device nodes also sounds very
appealing to me (particularly from a W^X sense)... There are not very
many grep hits on VM_EXEC in drivers/*, and none of the ones I looked
at seemed problematic.
Jason
next prev parent reply other threads:[~2019-04-22 12:51 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 11:07 [PATCH rdma-next 0/6] BAR mappings fixes in RDMA Leon Romanovsky
2019-04-16 11:07 ` [PATCH rdma-next 1/6] RDMA/mlx5: Do not allow the user to write to the clock page Leon Romanovsky
2019-04-16 11:07 ` [PATCH rdma-next 2/6] RDMA/mlx5: Use rdma_user_map_io for mapping BAR pages Leon Romanovsky
2019-04-16 11:07 ` [PATCH rdma-next 3/6] RDMA/ucontext: Do not allow BAR mappings to be executable Leon Romanovsky
2019-04-17 19:05 ` Ruhl, Michael J
2019-04-18 5:58 ` Jason Gunthorpe
2019-04-18 6:30 ` Kees Cook
2019-04-18 7:01 ` Jason Gunthorpe
2019-04-18 7:23 ` Kees Cook
2019-04-22 12:51 ` Jason Gunthorpe [this message]
2019-04-16 11:07 ` [PATCH rdma-next 4/6] RDMA/ucontext: Fix regression with disassociate Leon Romanovsky
2019-04-16 11:07 ` [PATCH mlx5-next 5/6] RDMA/mlx5: Use get_zeroed_page() for clock_info Leon Romanovsky
2019-04-16 11:07 ` [PATCH rdma-next 6/6] RDMA: Remove rdma_user_mmap_page Leon Romanovsky
2019-04-24 19:24 ` [PATCH rdma-next 0/6] BAR mappings fixes in RDMA Jason Gunthorpe
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