From: Evgenii Stepanov <eugenis@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-rdma@vger.kernel.org, linux-media@vger.kernel.org,
kvm@vger.kernel.org,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>,
Yishai Hadas <yishaih@mellanox.com>,
Felix Kuehling <Felix.Kuehling@amd.com>,
Alexander Deucher <Alexander.Deucher@amd.com>,
Christian Koenig <Christian.Koenig@amd.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Jens Wiklander <jens.wiklander@linaro.org>,
Alex Williamson <alex.williamson@redhat.com>,
Leon Romanovsky <leon@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Kostya Serebryany <kcc@google.com>, Lee Smith <Lee.Smith@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Jacob Bramley <Jacob.Bramley@arm.com>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Robin Murphy <robin.murphy@arm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Dave Martin <Dave.Martin@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Subject: Re: [PATCH v15 05/17] arms64: untag user pointers passed to memory syscalls
Date: Thu, 23 May 2019 21:23:13 -0700 [thread overview]
Message-ID: <CAFKCwrgk0+yR48Z5nhuZG5f7g==vRb4u+CS-4FS0mM7Eriavgw@mail.gmail.com> (raw)
In-Reply-To: <20190523090427.GA44383@arrakis.emea.arm.com>
On Thu, May 23, 2019 at 2:04 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> On Wed, May 22, 2019 at 02:16:57PM -0700, Evgenii Stepanov wrote:
> > On Wed, May 22, 2019 at 4:49 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > > On Mon, May 06, 2019 at 06:30:51PM +0200, Andrey Konovalov wrote:
> > > > This patch is a part of a series that extends arm64 kernel ABI to allow to
> > > > pass tagged user pointers (with the top byte set to something else other
> > > > than 0x00) as syscall arguments.
> > > >
> > > > This patch allows tagged pointers to be passed to the following memory
> > > > syscalls: brk, get_mempolicy, madvise, mbind, mincore, mlock, mlock2,
> > > > mmap, mmap_pgoff, mprotect, mremap, msync, munlock, munmap,
> > > > remap_file_pages, shmat and shmdt.
> > > >
> > > > This is done by untagging pointers passed to these syscalls in the
> > > > prologues of their handlers.
> > >
> > > I'll go through them one by one to see if we can tighten the expected
> > > ABI while having the MTE in mind.
> > >
> > > > diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
> > > > index b44065fb1616..933bb9f3d6ec 100644
> > > > --- a/arch/arm64/kernel/sys.c
> > > > +++ b/arch/arm64/kernel/sys.c
> > > > @@ -35,10 +35,33 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
> > > > {
> > > > if (offset_in_page(off) != 0)
> > > > return -EINVAL;
> > > > -
> > > > + addr = untagged_addr(addr);
> > > > return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
> > > > }
> > >
> > > If user passes a tagged pointer to mmap() and the address is honoured
> > > (or MAP_FIXED is given), what is the expected return pointer? Does it
> > > need to be tagged with the value from the hint?
> >
> > For HWASan the most convenient would be to use the tag from the hint.
> > But since in the TBI (not MTE) mode the kernel has no idea what
> > meaning userspace assigns to pointer tags, perhaps it should not try
> > to guess, and should return raw (zero-tagged) address instead.
>
> Then, just to relax the ABI for hwasan, shall we simply disallow tagged
> pointers on mmap() arguments? We can leave them in for
> mremap(old_address), madvise().
I think this would be fine. We should allow tagged in pointers in
mprotect though.
> > > With MTE, we may want to use this as a request for the default colour of
> > > the mapped pages (still under discussion).
> >
> > I like this - and in that case it would make sense to return the
> > pointer that can be immediately dereferenced without crashing the
> > process, i.e. with the matching tag.
>
> This came up from the Android investigation work where large memory
> allocations (using mmap) could be more efficiently pre-tagged by the
> kernel on page fault. Not sure about the implementation details yet.
>
> --
> Catalin
next prev parent reply other threads:[~2019-05-24 4:23 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 16:30 [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 01/17] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2019-05-29 14:49 ` Khalid Aziz
2019-05-06 16:30 ` [PATCH v15 02/17] arm64: untag user pointers in access_ok and __uaccess_mask_ptr Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 03/17] lib, arm64: untag user pointers in strn*_user Andrey Konovalov
2019-05-22 10:41 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 04/17] mm: add ksys_ wrappers to memory syscalls Andrey Konovalov
2019-05-22 10:56 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 05/17] arms64: untag user pointers passed " Andrey Konovalov
2019-05-22 11:49 ` Catalin Marinas
2019-05-22 21:16 ` Evgenii Stepanov
2019-05-23 9:04 ` Catalin Marinas
2019-05-24 4:23 ` Evgenii Stepanov [this message]
2019-05-24 15:41 ` Andrew Murray
2019-05-25 9:57 ` Catalin Marinas
2019-05-27 9:42 ` Catalin Marinas
2019-05-27 14:37 ` Catalin Marinas
2019-05-28 14:54 ` Andrew Murray
2019-05-28 15:40 ` Catalin Marinas
2019-05-28 15:56 ` Dave Martin
2019-05-28 16:34 ` Catalin Marinas
2019-05-29 12:42 ` Dave Martin
2019-05-29 13:23 ` Catalin Marinas
2019-05-29 15:18 ` Dave Martin
2019-05-28 23:33 ` Khalid Aziz
2019-05-29 14:20 ` Catalin Marinas
2019-05-29 19:16 ` Khalid Aziz
2019-05-30 15:11 ` Catalin Marinas
2019-05-30 16:05 ` Khalid Aziz
2019-05-30 16:57 ` Catalin Marinas
2019-05-28 13:05 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 06/17] mm: untag user pointers in do_pages_move Andrey Konovalov
2019-05-22 11:51 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 07/17] mm, arm64: untag user pointers in mm/gup.c Andrey Konovalov
2019-05-22 11:56 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 08/17] mm, arm64: untag user pointers in get_vaddr_frames Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 09/17] fs, arm64: untag user pointers in copy_mount_options Andrey Konovalov
2019-05-22 12:09 ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 10/17] fs, arm64: untag user pointers in fs/userfaultfd.c Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 11/17] drm/amdgpu, arm64: untag user pointers Andrey Konovalov
2019-05-07 16:43 ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 12/17] drm/radeon, arm64: untag user pointers in radeon_gem_userptr_ioctl Andrey Konovalov
2019-05-07 16:44 ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 13/17] IB, arm64: untag user pointers in ib_uverbs_(re)reg_mr() Andrey Konovalov
2019-05-06 19:50 ` Jason Gunthorpe
2019-05-07 6:33 ` Leon Romanovsky
2019-05-06 16:31 ` [PATCH v15 14/17] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get Andrey Konovalov
2019-05-24 13:13 ` Mauro Carvalho Chehab
2019-05-06 16:31 ` [PATCH v15 15/17] tee, arm64: untag user pointers in tee_shm_register Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 16/17] vfio/type1, arm64: untag user pointers in vaddr_get_pfn Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 17/17] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2019-05-22 14:16 ` Catalin Marinas
2019-05-31 14:21 ` Andrey Konovalov
2019-05-31 16:22 ` Catalin Marinas
2019-05-17 14:49 ` [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Catalin Marinas
2019-05-20 23:53 ` Evgenii Stepanov
2019-05-21 18:29 ` Catalin Marinas
2019-05-22 0:04 ` Kees Cook
2019-05-22 10:11 ` Catalin Marinas
2019-05-22 15:30 ` enh
2019-05-22 16:35 ` Catalin Marinas
2019-05-22 16:58 ` enh
2019-05-23 15:21 ` Catalin Marinas
2019-05-22 20:47 ` Kees Cook
2019-05-22 23:03 ` Evgenii Stepanov
2019-05-22 23:09 ` enh
2019-05-23 7:34 ` Catalin Marinas
2019-05-23 14:44 ` Catalin Marinas
2019-05-23 15:44 ` enh
2019-05-23 17:00 ` Catalin Marinas
2019-05-23 16:38 ` Kees Cook
2019-05-23 17:43 ` Catalin Marinas
2019-05-23 21:31 ` Kees Cook
2019-05-24 11:20 ` Catalin Marinas
2019-05-28 17:02 ` Catalin Marinas
2019-06-02 5:06 ` Kees Cook
2019-05-22 19:21 ` Kees Cook
2019-05-22 20:15 ` enh
2019-05-23 15:08 ` Catalin Marinas
2019-05-23 17:51 ` Khalid Aziz
2019-05-23 20:11 ` Catalin Marinas
2019-05-23 21:42 ` Khalid Aziz
2019-05-23 21:49 ` Khalid Aziz
2019-05-24 10:11 ` Catalin Marinas
2019-05-24 14:25 ` Khalid Aziz
2019-05-28 14:14 ` Andrey Konovalov
2019-05-29 6:11 ` Christoph Hellwig
2019-05-29 12:12 ` Catalin Marinas
2019-05-30 17:15 ` Catalin Marinas
2019-05-31 14:29 ` Andrey Konovalov
2019-05-31 16:19 ` Catalin Marinas
2019-05-31 16:24 ` Andrey Konovalov
2019-05-31 16:46 ` Catalin Marinas
2019-05-21 18:48 ` Jason Gunthorpe
2019-05-22 13:49 ` Dave Martin
2019-05-23 0:20 ` Jason Gunthorpe
2019-05-23 10:42 ` Dave Martin
2019-05-23 16:57 ` Catalin Marinas
2019-05-24 14:23 ` Dave Martin
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