linux-kernel - Re: [PATCH v8 3/8] arm64: untag user addresses in access_ok and __uaccess_mask

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Message-ID: <20181129182446.GJ22027@arrakis.emea.arm.com>
Date:   Thu, 29 Nov 2018 18:24:48 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>,
        Kees Cook <keescook@...omium.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chintan Pandya <cpandya@...eaurora.org>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Lee Smith <Lee.Smith@....com>,
        Kostya Serebryany <kcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Evgeniy Stepanov <eugenis@...gle.com>
Subject: Re: [PATCH v8 3/8] arm64: untag user addresses in access_ok and
 __uaccess_mask_ptr

On Thu, Nov 08, 2018 at 03:36:10PM +0100, Andrey Konovalov wrote:
> copy_from_user (and a few other similar functions) are used to copy data
> from user memory into the kernel memory or vice versa. Since a user can
> provided a tagged pointer to one of the syscalls that use copy_from_user,
> we need to correctly handle such pointers.
> 
> Do this by untagging user pointers in access_ok and in __uaccess_mask_ptr,
> before performing access validity checks.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>