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From: Andy Lutomirski <luto@kernel.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
	linux-arch <linux-arch@vger.kernel.org>, X86 ML <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. J. Lu" <hjl.tools@gmail.com>,
	"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>,
	mike.kravetz@oracle.com
Subject: Re: [PATCH 3/7] mm/mmap: Add IBT bitmap size to address space limit check
Date: Thu, 7 Jun 2018 11:39:12 -0700	[thread overview]
Message-ID: <CALCETrWNaA4rg3Q6-OShAt7Yp9VmyvyFOQtn6cAbrKMHiggGzg@mail.gmail.com> (raw)
In-Reply-To: <20180607143855.3681-4-yu-cheng.yu@intel.com>

On Thu, Jun 7, 2018 at 7:42 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
>
> The indirect branch tracking legacy bitmap takes a large address
> space.  This causes may_expand_vm() failure on the address limit
> check.  For a IBT-enabled task, add the bitmap size to the
> address limit.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> ---
>  arch/x86/include/uapi/asm/resource.h | 5 +++++
>  include/uapi/asm-generic/resource.h  | 3 +++
>  mm/mmap.c                            | 8 +++++++-
>  3 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/uapi/asm/resource.h b/arch/x86/include/uapi/asm/resource.h
> index 04bc4db8921b..0741b2a6101a 100644
> --- a/arch/x86/include/uapi/asm/resource.h
> +++ b/arch/x86/include/uapi/asm/resource.h
> @@ -1 +1,6 @@
> +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
> +#ifdef CONFIG_X86_INTEL_CET
> +#define rlimit_as_extra() current->thread.cet.ibt_bitmap_size
> +#endif
> +
>  #include <asm-generic/resource.h>
> diff --git a/include/uapi/asm-generic/resource.h b/include/uapi/asm-generic/resource.h
> index f12db7a0da64..8a7608a09700 100644
> --- a/include/uapi/asm-generic/resource.h
> +++ b/include/uapi/asm-generic/resource.h
> @@ -58,5 +58,8 @@
>  # define RLIM_INFINITY         (~0UL)
>  #endif
>
> +#ifndef rlimit_as_extra
> +#define rlimit_as_extra() 0
> +#endif
>
>  #endif /* _UAPI_ASM_GENERIC_RESOURCE_H */
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e7d1fcb7ec58..5c07f052bed7 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -3255,7 +3255,13 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
>   */
>  bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
>  {
> -       if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
> +       unsigned long as_limit = rlimit(RLIMIT_AS);
> +       unsigned long as_limit_plus = as_limit + rlimit_as_extra();
> +
> +       if (as_limit_plus > as_limit)
> +               as_limit = as_limit_plus;
> +

What happens if as_limit_plus overflows?  I guess it's probably okay here.

  reply	other threads:[~2018-06-07 18:39 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 14:38 [PATCH 0/7] Control Flow Enforcement - Part (4) Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 1/7] x86/cet: Add Kconfig option for user-mode Indirect Branch Tracking Yu-cheng Yu
2018-06-07 16:43   ` Randy Dunlap
2018-06-07 14:38 ` [PATCH 2/7] x86/cet: User-mode indirect branch tracking support Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 3/7] mm/mmap: Add IBT bitmap size to address space limit check Yu-cheng Yu
2018-06-07 18:39   ` Andy Lutomirski [this message]
2018-06-07 14:38 ` [PATCH 4/7] x86/cet: add arcp_prctl functions for indirect branch tracking Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 5/7] x86: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2018-06-07 20:50   ` Andy Lutomirski
2018-06-07 22:03     ` H.J. Lu
2018-06-07 23:00       ` Andy Lutomirski
2018-06-08  0:31         ` H.J. Lu
2018-06-08  0:47           ` Andy Lutomirski
2018-06-07 14:38 ` [PATCH 6/7] tools: Add cetcmd Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 7/7] x86/cet: Add PTRACE interface for CET Yu-cheng Yu
2018-06-07 18:32   ` Andy Lutomirski

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