From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: robert.foss@collabora.com
Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
vbabka@suse.cz, mhocko@suse.com, mingo@kernel.org,
dave.hansen@linux.intel.com, hannes@cmpxchg.org,
dan.j.williams@intel.com, iamjoonsoo.kim@lge.com,
acme@redhat.com, keescook@chromium.org,
mgorman@techsingularity.net, atomlin@redhat.com,
hughd@google.com, dyoung@redhat.com, viro@zeniv.linux.org.uk,
dcashman@google.com, w@1wt.eu, idryomov@gmail.com,
yang.shi@linaro.org, wad@chromium.org, vkuznets@redhat.com,
vdavydov@virtuozzo.com, vitalywool@gmail.com, oleg@redhat.com,
gang.chen.5i5j@gmail.com, koct9i@gmail.com, aarcange@redhat.com,
aryabinin@virtuozzo.com, kuleshovmail@gmail.com,
minchan@kernel.org, mguzik@redhat.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, krasin@google.com,
Roland McGrath <mcgrathr@chromium.org>,
Mandeep Singh Baines <msb@chromium.org>,
Ben Zhang <benzh@chromium.org>,
Filipe Brandenburger <filbranden@chromium.org>
Subject: Re: [PATCH v1] mm, sysctl: Add sysctl for controlling VM_MAYEXEC taint
Date: Sat, 27 Aug 2016 00:32:27 +0300 [thread overview]
Message-ID: <20160826213227.GA11393@node.shutemov.name> (raw)
In-Reply-To: <1472229004-9658-1-git-send-email-robert.foss@collabora.com>
On Fri, Aug 26, 2016 at 12:30:04PM -0400, robert.foss@collabora.com wrote:
> From: Will Drewry <wad@chromium.org>
>
> This patch proposes a sysctl knob that allows a privileged user to
> disable ~VM_MAYEXEC tainting when mapping in a vma from a MNT_NOEXEC
> mountpoint. It does not alter the normal behavior resulting from
> attempting to directly mmap(PROT_EXEC) a vma (-EPERM) nor the behavior
> of any other subsystems checking MNT_NOEXEC.
Wouldn't it be equal to remounting all filesystems without noexec from
attacker POV? It's hardly a fence to make additional mprotect(PROT_EXEC)
call, before starting executing code from such filesystems.
If administrator of the system wants this, he can just mount filesystem
without noexec, no new kernel code required. And it's more fine-grained
than this.
So, no, I don't think we should add knob like this. Unless I miss
something.
NAK.
> It is motivated by a common /dev/shm, /tmp usecase. There are few
> facilities for creating a shared memory segment that can be remapped in
> the same process address space with different permissions.
What about using memfd_create(2) for such cases? You'll get a file
descriptor from in-kernel tmpfs (shm_mnt) which is not exposed to
userspace for remount as noexec.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2016-08-26 21:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-26 16:30 [PATCH v1] mm, sysctl: Add sysctl for controlling VM_MAYEXEC taint robert.foss
2016-08-26 17:17 ` kbuild test robot
2016-08-26 21:32 ` Kirill A. Shutemov [this message]
2016-08-29 15:25 ` Will Drewry
2016-08-29 15:31 ` Robert Foss
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