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From: Catalin Marinas <catalin.marinas@arm.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	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,
	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>,
	Evgeniy Stepanov <eugenis@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>,
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	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: Wed, 22 May 2019 12:49:10 +0100
Message-ID: <20190522114910.emlckebwzv2qz42i@mbp> (raw)
In-Reply-To: <00eb4c63fefc054e2c8d626e8fedfca11d7c2600.1557160186.git.andreyknvl@google.com>

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?

With MTE, we may want to use this as a request for the default colour of
the mapped pages (still under discussion).

> +SYSCALL_DEFINE6(arm64_mmap_pgoff, unsigned long, addr, unsigned long, len,
> +		unsigned long, prot, unsigned long, flags,
> +		unsigned long, fd, unsigned long, pgoff)
> +{
> +	addr = untagged_addr(addr);
> +	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
> +}

We don't have __NR_mmap_pgoff on arm64.

> +SYSCALL_DEFINE5(arm64_mremap, unsigned long, addr, unsigned long, old_len,
> +		unsigned long, new_len, unsigned long, flags,
> +		unsigned long, new_addr)
> +{
> +	addr = untagged_addr(addr);
> +	new_addr = untagged_addr(new_addr);
> +	return ksys_mremap(addr, old_len, new_len, flags, new_addr);
> +}

Similar comment as for mmap(), do we want the tag from new_addr to be
preserved? In addition, should we check that the two tags are identical
or mremap() should become a way to repaint a memory region?

> +SYSCALL_DEFINE2(arm64_munmap, unsigned long, addr, size_t, len)
> +{
> +	addr = untagged_addr(addr);
> +	return ksys_munmap(addr, len);
> +}

This looks fine.

> +SYSCALL_DEFINE1(arm64_brk, unsigned long, brk)
> +{
> +	brk = untagged_addr(brk);
> +	return ksys_brk(brk);
> +}

I wonder whether brk() should simply not accept tags, and should not
return them (similar to the prctl(PR_SET_MM) discussion). We could
document this in the ABI requirements.

> +SYSCALL_DEFINE5(arm64_get_mempolicy, int __user *, policy,
> +		unsigned long __user *, nmask, unsigned long, maxnode,
> +		unsigned long, addr, unsigned long, flags)
> +{
> +	addr = untagged_addr(addr);
> +	return ksys_get_mempolicy(policy, nmask, maxnode, addr, flags);
> +}
> +
> +SYSCALL_DEFINE3(arm64_madvise, unsigned long, start,
> +		size_t, len_in, int, behavior)
> +{
> +	start = untagged_addr(start);
> +	return ksys_madvise(start, len_in, behavior);
> +}
> +
> +SYSCALL_DEFINE6(arm64_mbind, unsigned long, start, unsigned long, len,
> +		unsigned long, mode, const unsigned long __user *, nmask,
> +		unsigned long, maxnode, unsigned int, flags)
> +{
> +	start = untagged_addr(start);
> +	return ksys_mbind(start, len, mode, nmask, maxnode, flags);
> +}
> +
> +SYSCALL_DEFINE2(arm64_mlock, unsigned long, start, size_t, len)
> +{
> +	start = untagged_addr(start);
> +	return ksys_mlock(start, len, VM_LOCKED);
> +}
> +
> +SYSCALL_DEFINE2(arm64_mlock2, unsigned long, start, size_t, len)
> +{
> +	start = untagged_addr(start);
> +	return ksys_mlock(start, len, VM_LOCKED);
> +}
> +
> +SYSCALL_DEFINE2(arm64_munlock, unsigned long, start, size_t, len)
> +{
> +	start = untagged_addr(start);
> +	return ksys_munlock(start, len);
> +}
> +
> +SYSCALL_DEFINE3(arm64_mprotect, unsigned long, start, size_t, len,
> +		unsigned long, prot)
> +{
> +	start = untagged_addr(start);
> +	return ksys_mprotect_pkey(start, len, prot, -1);
> +}
> +
> +SYSCALL_DEFINE3(arm64_msync, unsigned long, start, size_t, len, int, flags)
> +{
> +	start = untagged_addr(start);
> +	return ksys_msync(start, len, flags);
> +}
> +
> +SYSCALL_DEFINE3(arm64_mincore, unsigned long, start, size_t, len,
> +		unsigned char __user *, vec)
> +{
> +	start = untagged_addr(start);
> +	return ksys_mincore(start, len, vec);
> +}

These look fine.

> +SYSCALL_DEFINE5(arm64_remap_file_pages, unsigned long, start,
> +		unsigned long, size, unsigned long, prot,
> +		unsigned long, pgoff, unsigned long, flags)
> +{
> +	start = untagged_addr(start);
> +	return ksys_remap_file_pages(start, size, prot, pgoff, flags);
> +}

While this has been deprecated for some time, I presume user space still
invokes it?

> +SYSCALL_DEFINE3(arm64_shmat, int, shmid, char __user *, shmaddr, int, shmflg)
> +{
> +	shmaddr = untagged_addr(shmaddr);
> +	return ksys_shmat(shmid, shmaddr, shmflg);
> +}
> +
> +SYSCALL_DEFINE1(arm64_shmdt, char __user *, shmaddr)
> +{
> +	shmaddr = untagged_addr(shmaddr);
> +	return ksys_shmdt(shmaddr);
> +}

Do we actually want to allow shared tagged memory? Who's going to tag
it? If not, we can document it as not supported.

-- 
Catalin

  reply index

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 [this message]
2019-05-22 21:16     ` Evgenii Stepanov
2019-05-23  9:04       ` Catalin Marinas
2019-05-24  4:23         ` Evgenii Stepanov
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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