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From: Catalin Marinas <catalin.marinas@arm.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	linux-doc@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Ingo Molnar <mingo@kernel.org>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Dmitry Vyukov <dvyukov@google.com>,
	Bart Van Assche <bart.vanassche@wdc.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Evgeniy Stepanov <eugenis@google.com>,
	Kees Cook <keescook@chromium.org>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Lee Smith <Lee.Smith@arm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Kostya Serebryany <kcc@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	James Morse <james.morse@arm.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Zi Yan <zi.yan@cs.rutgers.edu>
Subject: Re: [PATCH 4/6] mm, arm64: untag user addresses in mm/gup.c
Date: Tue, 8 May 2018 16:11:38 +0100	[thread overview]
Message-ID: <20180508151137.zguepljs3pa7xv5g@armageddon.cambridge.arm.com> (raw)
In-Reply-To: <CAAeHK+yTbmZfkeNbqbo+J90zsjsM99rwnYBGfQBxphHMMfgD7A@mail.gmail.com>

On Wed, May 02, 2018 at 07:25:17PM +0200, Andrey Konovalov wrote:
> On Wed, May 2, 2018 at 5:36 PM, Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> > On Wed, May 02, 2018 at 02:38:42PM +0000, Andrey Konovalov wrote:
> >> > Does having a tagged address here makes any difference? I couldn't hit a
> >> > failure with my simple tests (LD_PRELOAD a library that randomly adds
> >> > tags to pointers returned by malloc).
> >>
> >> I think you're right, follow_page_mask is only called from
> >> __get_user_pages, which already untagged the address. I'll remove
> >> untagging here.
> >
> > It also called from follow_page(). Have you covered all its callers?
> 
> Oh, missed that, will take a look.
> 
> Thinking about that, would it make sense to add untagging to find_vma
> (and others) instead of trying to cover all find_vma callers?

I don't think adding the untagging to find_vma() is sufficient. In many
cases the caller does a subsequent check like 'start < vma->vm_start'
(see sys_msync() as an example, there are a few others as well). What I
did in my tests was a WARN_ON_ONCE() in find_vma() if the address is
tagged.

-- 
Catalin

  parent reply	other threads:[~2018-05-08 15:11 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 18:53 [PATCH 0/6] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-04-18 18:53 ` [PATCH 1/6] arm64: add type casts to untagged_addr macro Andrey Konovalov
2018-04-18 18:53 ` [PATCH 2/6] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2018-04-18 18:53 ` [PATCH 3/6] arm64: untag user addresses in copy_from_user and others Andrey Konovalov
2018-04-26 15:47   ` Catalin Marinas
2018-05-02 15:29     ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 4/6] mm, arm64: untag user addresses in mm/gup.c Andrey Konovalov
2018-04-26 17:47   ` Catalin Marinas
2018-05-02 14:38     ` Andrey Konovalov
2018-05-02 15:36       ` Kirill A. Shutemov
2018-05-02 17:25         ` Andrey Konovalov
2018-05-03 14:09           ` Andrey Konovalov
2018-05-03 15:24             ` Kirill A. Shutemov
2018-05-03 16:51               ` Andrey Konovalov
2018-05-08 15:11           ` Catalin Marinas [this message]
2018-05-11 12:36             ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 5/6] lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user Andrey Konovalov
2018-04-18 18:53 ` [PATCH 6/6] arm64: update Documentation/arm64/tagged-pointers.txt Andrey Konovalov
2018-04-19  9:33 ` [PATCH 0/6] arm64: untag user pointers passed to the kernel Kirill A. Shutemov
2018-04-25 14:45   ` Andrey Konovalov
2018-04-26 17:56     ` Catalin Marinas

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